more house keeping

ARCHITECTURE.md

@@ -1,426 +0,0 @@
-## JormunDB Architecture
-
-This document explains the internal architecture of JormunDB, including design decisions, storage formats, and the arena-per-request memory management pattern.
-
-## Table of Contents
-
-- [Overview](#overview)
-- [Why Odin?](#why-odin)
-- [Memory Management](#memory-management)
-- [Storage Format](#storage-format)
-- [Module Structure](#module-structure)
-- [Request Flow](#request-flow)
-- [Concurrency Model](#concurrency-model)
-
-## Overview
-
-JormunDB is a DynamoDB-compatible database server that speaks the DynamoDB wire protocol. It uses RocksDB for persistent storage and is written in Odin for elegant memory management.
-
-### Key Design Goals
-
-1. **Zero allocation ceremony** - No explicit `defer free()` or error handling for every allocation
-2. **Binary storage** - Efficient TLV encoding instead of JSON
-3. **API compatibility** - Drop-in replacement for DynamoDB
-4. **Performance** - RocksDB-backed with efficient key encoding
-
-## Why Odin?
-
-The original implementation in Zig suffered from explicit allocator threading:
-
-```zig
-// Zig version - explicit allocator everywhere
-fn handleRequest(allocator: std.mem.Allocator, request: []const u8) !Response {
-    const parsed = try parseJson(allocator, request);
-    defer parsed.deinit(allocator);
-
-    const item = try storage.getItem(allocator, parsed.table_name, parsed.key);
-    defer if (item) |i| freeItem(allocator, i);
-
-    const response = try serializeResponse(allocator, item);
-    defer allocator.free(response);
-
-    return response; // Wait, we deferred the free!
-}
-```
-
-Odin's context allocator system eliminates this:
-
-```odin
-// Odin version - implicit context allocator
-handle_request :: proc(request: []byte) -> Response {
-    // All allocations use context.allocator automatically
-    parsed := parse_json(request)
-    item := storage_get_item(parsed.table_name, parsed.key)
-    response := serialize_response(item)
-
-    return response
-    // Everything freed when arena is destroyed
-}
-```
-
-## Memory Management
-
-JormunDB uses a two-allocator strategy:
-
-### 1. Arena Allocator (Request-Scoped)
-
-Every HTTP request gets its own arena:
-
-```odin
-handle_connection :: proc(conn: net.TCP_Socket) {
-    // Create arena for this request (4MB)
-    arena: mem.Arena
-    mem.arena_init(&arena, make([]byte, mem.Megabyte * 4))
-    defer mem.arena_destroy(&arena)
-
-    // Set context allocator
-    context.allocator = mem.arena_allocator(&arena)
-
-    // All downstream code uses context.allocator
-    request := parse_http_request(conn)    // uses arena
-    response := handle_request(request)     // uses arena
-    send_response(conn, response)           // uses arena
-
-    // Arena is freed here - everything cleaned up automatically
-}
-```
-
-**Benefits:**
-- No individual `free()` calls needed
-- No `errdefer` cleanup
-- No use-after-free bugs
-- No memory leaks from forgotten frees
-- Predictable performance (no GC pauses)
-
-### 2. Default Allocator (Long-Lived Data)
-
-The default allocator (typically `context.allocator` at program start) is used for:
-
-- Table metadata
-- Table locks (sync.RW_Mutex)
-- Engine state
-- Items returned from storage layer (copied to request arena when needed)
-
-## Storage Format
-
-### Binary Keys (Varint-Prefixed Segments)
-
-All keys use varint length prefixes for space efficiency:
-
-```
-Meta key:  [0x01][len][table_name]
-Data key:  [0x02][len][table_name][len][pk_value][len][sk_value]?
-GSI key:   [0x03][len][table_name][len][index_name][len][gsi_pk][len][gsi_sk]?
-LSI key:   [0x04][len][table_name][len][index_name][len][pk][len][lsi_sk]
-```
-
-**Example Data Key:**
-```
-Table: "Users"
-PK: "user:123"
-SK: "profile"
-
-Encoded:
-[0x02]          // Entity type (Data)
-[0x05]          // Table name length (5)
-Users           // Table name bytes
-[0x08]          // PK length (8)
-user:123        // PK bytes
-[0x07]          // SK length (7)
-profile         // SK bytes
-```
-
-### Item Encoding (TLV Format)
-
-Items use Tag-Length-Value encoding for space efficiency:
-
-```
-Format:
-[attr_count:varint]
-  [name_len:varint][name:bytes][type_tag:u8][value_len:varint][value:bytes]...
-
-Type Tags:
-  String  = 0x01    Number = 0x02    Binary = 0x03
-  Bool    = 0x04    Null   = 0x05
-  SS      = 0x10    NS     = 0x11    BS     = 0x12
-  List    = 0x20    Map    = 0x21
-```
-
-**Example Item:**
-```json
-{
-  "id": {"S": "user123"},
-  "age": {"N": "30"}
-}
-```
-
-Encoded as:
-```
-[0x02]              // 2 attributes
-  [0x02]            // name length (2)
-  id                // name bytes
-  [0x01]            // type tag (String)
-  [0x07]            // value length (7)
-  user123           // value bytes
-
-  [0x03]            // name length (3)
-  age               // name bytes
-  [0x02]            // type tag (Number)
-  [0x02]            // value length (2)
-  30                // value bytes (stored as string)
-```
-
-## Module Structure
-
-```
-jormundb/
-├── main.odin           # Entry point, HTTP server
-├── rocksdb/            # RocksDB C FFI bindings
-│   └── rocksdb.odin    # db_open, db_put, db_get, etc.
-├── dynamodb/           # DynamoDB protocol implementation
-│   ├── types.odin      # Core types (Attribute_Value, Item, Key, etc.)
-│   ├── json.odin       # DynamoDB JSON parsing/serialization
-│   ├── storage.odin    # Storage engine (CRUD, scan, query)
-│   └── handler.odin    # HTTP request handlers
-├── key_codec/          # Binary key encoding
-│   └── key_codec.odin  # build_data_key, decode_data_key, etc.
-└── item_codec/         # Binary TLV item encoding
-    └── item_codec.odin # encode, decode
-```
-
-## Request Flow
-
-```
-1. HTTP POST / arrives
-   ↓
-2. Create arena allocator (4MB)
-   Set context.allocator = arena_allocator
-   ↓
-3. Parse HTTP headers
-   Extract X-Amz-Target → Operation
-   ↓
-4. Parse JSON body
-   Convert DynamoDB JSON → internal types
-   ↓
-5. Route to handler (e.g., handle_put_item)
-   ↓
-6. Storage engine operation
-   - Build binary key
-   - Encode item to TLV
-   - RocksDB put/get/delete
-   ↓
-7. Build response
-   - Serialize item to DynamoDB JSON
-   - Format HTTP response
-   ↓
-8. Send response
-   ↓
-9. Destroy arena
-   All request memory freed automatically
-```
-
-## Concurrency Model
-
-### Table-Level RW Locks
-
-Each table has a reader-writer lock:
-
-```odin
-Storage_Engine :: struct {
-    db:                 rocksdb.DB,
-    table_locks:        map[string]^sync.RW_Mutex,
-    table_locks_mutex:  sync.Mutex,
-}
-```
-
-**Read Operations** (GetItem, Query, Scan):
-- Acquire shared lock
-- Multiple readers can run concurrently
-- Writers are blocked
-
-**Write Operations** (PutItem, DeleteItem, UpdateItem):
-- Acquire exclusive lock
-- Only one writer at a time
-- All readers are blocked
-
-### Thread Safety
-
-- RocksDB handles are thread-safe (column family-based)
-- Table metadata is protected by locks
-- Request arenas are thread-local (no sharing)
-
-## Error Handling
-
-Odin uses explicit error returns via `or_return`:
-
-```odin
-// Odin error handling
-parse_json :: proc(data: []byte) -> (Item, bool) {
-    parsed := json.parse(data) or_return
-    item := json_to_item(parsed) or_return
-    return item, true
-}
-
-// Usage
-item := parse_json(request.body) or_else {
-    return error_response(.ValidationException, "Invalid JSON")
-}
-```
-
-No exceptions, no panic-recover patterns. Every error path is explicit.
-
-## DynamoDB Wire Protocol
-
-### Request Format
-
-```
-POST / HTTP/1.1
-X-Amz-Target: DynamoDB_20120810.PutItem
-Content-Type: application/x-amz-json-1.0
-
-{
-  "TableName": "Users",
-  "Item": {
-    "id": {"S": "user123"},
-    "name": {"S": "Alice"}
-  }
-}
-```
-
-### Response Format
-
-```
-HTTP/1.1 200 OK
-Content-Type: application/x-amz-json-1.0
-x-amzn-RequestId: local-request-id
-
-{}
-```
-
-### Error Format
-
-```json
-{
-  "__type": "com.amazonaws.dynamodb.v20120810#ResourceNotFoundException",
-  "message": "Table not found"
-}
-```
-
-## Performance Characteristics
-
-### Time Complexity
-
-| Operation | Complexity | Notes |
-|-----------|-----------|-------|
-| PutItem | O(log n) | RocksDB LSM tree insert |
-| GetItem | O(log n) | RocksDB point lookup |
-| DeleteItem | O(log n) | RocksDB deletion |
-| Query | O(log n + m) | n = items in table, m = result set |
-| Scan | O(n) | Full table scan |
-
-### Space Complexity
-
-- Binary keys: ~20-100 bytes (vs 50-200 bytes JSON)
-- Binary items: ~30% smaller than JSON
-- Varint encoding saves space on small integers
-
-### Benchmarks (Expected)
-
-Based on Zig version performance:
-
-```
-Operation          Throughput      Latency (p50)
-PutItem            ~5,000/sec      ~0.2ms
-GetItem            ~7,000/sec      ~0.14ms
-Query (1 item)     ~8,000/sec      ~0.12ms
-Scan (1000 items)  ~20/sec         ~50ms
-```
-
-## Future Enhancements
-
-### Planned Features
-
-1. **UpdateExpression** - SET/REMOVE/ADD/DELETE operations
-2. **FilterExpression** - Post-query filtering
-3. **ProjectionExpression** - Return subset of attributes
-4. **Global Secondary Indexes** - Query by non-key attributes
-5. **Local Secondary Indexes** - Alternate sort keys
-6. **BatchWriteItem** - Batch mutations
-7. **BatchGetItem** - Batch reads
-8. **Transactions** - ACID multi-item operations
-
-### Optimization Opportunities
-
-1. **Connection pooling** - Reuse HTTP connections
-2. **Bloom filters** - Faster negative lookups
-3. **Compression** - LZ4/Zstd on large items
-4. **Caching layer** - Hot item cache
-5. **Parallel scan** - Segment-based scanning
-
-## Debugging
-
-### Enable Verbose Logging
-
-```bash
-make run VERBOSE=1
-```
-
-### Inspect RocksDB
-
-```bash
-# Use ldb tool to inspect database
-ldb --db=./data scan
-ldb --db=./data get <key_hex>
-```
-
-### Memory Profiling
-
-Odin's tracking allocator can detect leaks:
-
-```odin
-when ODIN_DEBUG {
-    track: mem.Tracking_Allocator
-    mem.tracking_allocator_init(&track, context.allocator)
-    context.allocator = mem.tracking_allocator(&track)
-
-    defer {
-        for _, leak in track.allocation_map {
-            fmt.printfln("Leaked %d bytes at %p", leak.size, leak.location)
-        }
-    }
-}
-```
-
-## Migration from Zig Version
-
-The Zig version (ZynamoDB) used the same binary storage format, so existing RocksDB databases can be read by JormunDB without migration.
-
-### Compatibility
-
-- ✅ Binary key format (byte-compatible)
-- ✅ Binary item format (byte-compatible)
-- ✅ Table metadata (JSON, compatible)
-- ✅ HTTP wire protocol (identical)
-
-### Breaking Changes
-
-None - JormunDB can open ZynamoDB databases directly.
-
----
-
-## Contributing
-
-When contributing to JormunDB:
-
-1. **Use the context allocator** - All request-scoped allocations should use `context.allocator`
-2. **Avoid manual frees** - Let the arena handle it
-3. **Long-lived data** - Use the default allocator explicitly
-4. **Test thoroughly** - Run `make test` before committing
-5. **Format code** - Run `make fmt` before committing
-
-## References
-
-- [Odin Language](https://odin-lang.org/)
-- [RocksDB Wiki](https://github.com/facebook/rocksdb/wiki)
-- [DynamoDB API Reference](https://docs.aws.amazon.com/amazondynamodb/latest/APIReference/)
-- [Varint Encoding](https://developers.google.com/protocol-buffers/docs/encoding#varints)

Makefile

@@ -16,6 +16,8 @@ CXX := g++
 AR  := ar
 CXXFLAGS := -O2 -fPIC -std=c++20 $(INCLUDE_PATH)
 
+# name of the docker compose file for the python tests
+SDK_TEST_COMPOSE := docker-compose-python-sdk-test.yaml
 
 # RocksDB and compression libraries
 ROCKSDB_LIBS := -lrocksdb -lstdc++ -lsnappy -llz4 -lzstd -lz -lbz2
@@ -145,35 +147,6 @@ check-deps:
 	@pkg-config --exists rocksdb || (echo "$(RED)✗ RocksDB not found$(NC)" && exit 1)
 	@echo "$(GREEN)✓ All dependencies found$(NC)"
 
-# AWS CLI test commands
-aws-test: run &
-	@sleep 2
-	@echo "$(BLUE)Testing with AWS CLI...$(NC)"
-	@echo "\n$(YELLOW)Creating table...$(NC)"
-	@aws dynamodb create-table \
-		--endpoint-url http://localhost:$(PORT) \
-		--table-name TestTable \
-		--key-schema AttributeName=pk,KeyType=HASH \
-		--attribute-definitions AttributeName=pk,AttributeType=S \
-		--billing-mode PAY_PER_REQUEST || true
-	@echo "\n$(YELLOW)Listing tables...$(NC)"
-	@aws dynamodb list-tables --endpoint-url http://localhost:$(PORT)
-	@echo "\n$(YELLOW)Putting item...$(NC)"
-	@aws dynamodb put-item \
-		--endpoint-url http://localhost:$(PORT) \
-		--table-name TestTable \
-		--item '{"pk":{"S":"test1"},"data":{"S":"hello world"}}'
-	@echo "\n$(YELLOW)Getting item...$(NC)"
-	@aws dynamodb get-item \
-		--endpoint-url http://localhost:$(PORT) \
-		--table-name TestTable \
-		--key '{"pk":{"S":"test1"}}'
-	@echo "\n$(YELLOW)Scanning table...$(NC)"
-	@aws dynamodb scan \
-		--endpoint-url http://localhost:$(PORT) \
-		--table-name TestTable
-	@echo "\n$(GREEN)✓ AWS CLI test complete$(NC)"
-
 # Development workflow
 dev: clean build run
 
@@ -198,7 +171,6 @@ help:
 	@echo ""
 	@echo "$(GREEN)Test Commands:$(NC)"
 	@echo "  make test           - Run unit tests"
-	@echo "  make aws-test       - Test with AWS CLI commands"
 	@echo ""
 	@echo "$(GREEN)Utility Commands:$(NC)"
 	@echo "  make fmt            - Format source code"

QUICKSTART.md

@@ -404,7 +404,6 @@ brew upgrade odin  # macOS
 
 ## Next Steps
 
-- Read [ARCHITECTURE.md](ARCHITECTURE.md) for internals
 - Check [TODO.md](TODO.md) for implementation status
 - Browse source code in `dynamodb/`, `rocksdb/`, etc.
 

README.md

@@ -16,7 +16,7 @@
 
 JormunDB is a Self-Hosted DynamoDB replacement that speaks the DynamoDB wire protocol. Point your AWS SDK or CLI at it and use it as a drop-in replacement.
 
-**Why Odin?** The original Zig implementation suffered from explicit allocator threading. Where every function ended up needing an `allocator` parameter and every allocation needed `errdefer` cleanup. Odin's implicit context allocator system eliminates this ceremony. Just one `context.allocator = arena_allocator` at the request handler entry and everything downstream just works.
+**Why Odin?** The original Zig implementation suffered from explicit allocator threading. Where every function ended up needing an `allocator` parameter and every allocation needed `errdefer` cleanup. Odin's implicit context allocator system eliminates this ceremony. Just one `context.allocator = arena_allocator` at the request handler entry and it feels more like working with ctx in Go instead of filling out tax forms.
 
 ## Features
 
@@ -119,23 +119,6 @@ Binary encoding → Disk
 JSON response → Client
 ```
 
-### Module Structure
-
-```
-jormundb/
-├── rocksdb/            - C FFI bindings to librocksdb
-├── rocksdb_shim/       - C++ FFI bindings to librocksdb (so we can use the WAL helper functions)
-├── dynamodb/           - Core types and operations
-│   ├── types.odin      - AttributeValue, Item, Key, etc.
-│   ├── json.odin       - DynamoDB JSON serialization
-│   ├── storage.odin    - Storage engine with RocksDB
-│   ├── key_codec.odin  - Binary key encoding
-│   ├── item_codec.odin - Binary TLV item encoding
-│   └── handler.odin    - HTTP request handlers
-├── http.odin           - HTTP Server
-└── main.odin           - HTTP Router and handler (entry point)
-```
-
 ### Storage Format
 
 **Keys** (varint-length-prefixed segments):
@@ -206,16 +189,38 @@ make run PORT=9000 DATA_DIR=/tmp/db VERBOSE=1
 
 ## Performance
 
-From benchmarks on the original Zig version (Odin expected to be similar or better):
+Benchmarked on single node localhost, 1000 iterations per test.
 
-```
+### Basic Operations
-Sequential Writes     |      10000 ops |   245.32 ms |    40765 ops/sec
+
-Random Reads          |      10000 ops |   312.45 ms |    32006 ops/sec
+| Operation | Throughput | Avg Latency | P95 Latency | P99 Latency |
-Batch Writes          |      10000 ops |    89.23 ms |   112071 ops/sec
+|-----------|------------|-------------|-------------|-------------|
-PutItem               |       5000 ops |   892.34 ms |     5604 ops/sec
+| **PutItem** | 1,021 ops/sec | 0.98ms | 1.02ms | 1.64ms |
-GetItem               |       5000 ops |   678.91 ms |     7365 ops/sec
+| **GetItem** | 1,207 ops/sec | 0.83ms | 0.90ms | 1.14ms |
-Scan (full table)     |       5000 ops |   234.56 ms |    21320 ops/sec
+| **Query** | 1,002 ops/sec | 1.00ms | 1.11ms | 1.85ms |
-```
+| **Scan** (100 items) | 18,804 ops/sec | 0.05ms | - | - |
+| **DeleteItem** | 1,254 ops/sec | 0.80ms | - | - |
+
+### Batch Operations
+
+| Operation | Throughput | Batch Size |
+|-----------|------------|------------|
+| **BatchWriteItem** | 9,297 ops/sec | 25 items |
+| **BatchGetItem** | 9,113 ops/sec | 25 items |
+
+### Concurrent Operations
+
+| Workers | Throughput | Avg Latency | P95 Latency | P99 Latency |
+|---------|------------|-------------|-------------|-------------|
+| **10 concurrent** | 1,286 ops/sec | 7.70ms | 15.16ms | 19.72ms |
+
+### Large Payloads
+
+| Payload Size | Throughput | Avg Latency |
+|--------------|------------|-------------|
+| **10KB** | 522 ops/sec | 1.91ms |
+| **50KB** | 166 ops/sec | 6.01ms |
+| **100KB** | 96 ops/sec | 10.33ms |
 
 ## API Compatibility
 
@@ -230,17 +235,17 @@ Scan (full table)     |       5000 ops |   234.56 ms |    21320 ops/sec
 - ✅ DeleteItem
 - ✅ Query (with KeyConditionExpression)
 - ✅ Scan (with pagination)
+- ✅ ConditionExpression
+- ✅ FilterExpression
+- ✅ ProjectionExpression
+- ✅ BatchWriteItem
+- ✅ BatchGetItem
+- ✅ Global Secondary Indexes
 
 ### Coming Soon
 
-- ⏳ UpdateItem (with UpdateExpression)
+- ⏳ UpdateItem (works but needs UPDATED_NEW/UPDATED_OLD response filtering to work for full Dynamo Parity)
-- ⏳ BatchWriteItem
-- ⏳ BatchGetItem
-- ⏳ Global Secondary Indexes
 - ⏳ Local Secondary Indexes
-- ⏳ ConditionExpression
-- ⏳ FilterExpression
-- ⏳ ProjectionExpression
 
 ## Configuration
 

TODO.md

@@ -1,29 +1,14 @@
 # JormunDB (Odin rewrite) — TODO
 
-This tracks the rewrite from Zig (ZynamoDB) → Odin (JormunDB), and what's left to stabilize + extend.
+This tracks what's left to stabilize + extend the project
 
-## Status Snapshot
-
-### ✅ Ported / Working (core)
-- [x] Project layout + Makefile targets (build/run/test/fmt)
-- [x] RocksDB bindings / integration
-- [x] Core DynamoDB types (AttributeValue / Item / Key / TableDescription, etc.)
-- [x] Binary key codec (varint length-prefixed segments)
-- [x] Binary item codec (TLV encoding / decoding)
-- [x] Storage engine: tables + CRUD + scan/query plumbing
-- [x] Table-level RW locks (read ops shared / write ops exclusive)
-- [x] HTTP server + request routing via `X-Amz-Target`
-- [x] DynamoDB JSON (parse + serialize)
-- [x] Expression parsing for Query key conditions (basic support)
-
----
 
 ## Now (MVP correctness + polish)
 Goal: "aws cli works reliably for CreateTable/ListTables/PutItem/GetItem/DeleteItem/Scan/Query" with correct DynamoDB-ish responses.
 
 ### 1) HTTP + routing hardening
 - [ ] Audit request parsing boundaries:
-  - Max body size enforcement (config exists, need to verify enforcement path)
+  - Max body size enforcement — **DONE**
   - Missing/invalid headers → correct DynamoDB error types
   - Content-Type handling (be permissive but consistent)
 - [x] Ensure **all request-scoped allocations** come from the request arena (no accidental long-lived allocs)
@@ -62,21 +47,11 @@ Goal: "aws cli works reliably for CreateTable/ListTables/PutItem/GetItem/DeleteI
 - [x] Expand operator coverage: BETWEEN and begins_with are implemented in parser
 - [x] **Sort key condition filtering in query** — **DONE**: `query()` now accepts optional `Sort_Key_Condition` and applies it (=, <, <=, >, >=, BETWEEN, begins_with)
 
----
+### 5) Service Features
+- [ ] Configuration settings like environment variables for defining users and credentials
+- [ ] Configuration settings for setting up master and replica nodes
 
-## Next (feature parity with Zig + API completeness)
+### 6) Test coverage / tooling
-### 5) UpdateItem / conditional logic groundwork
-- [x] `UpdateItem` handler registered in router (currently returns clear "not yet supported" error)
-- [ ] Implement `UpdateItem` (initially minimal: SET for scalar attrs)
-- [ ] Add `ConditionExpression` support for Put/Delete/Update (start with simple comparisons)
-- [ ] Define internal "update plan" representation (parsed ops → applied mutations)
-
-### 6) Response completeness / options
-- [ ] `ReturnValues` handling where relevant (NONE/ALL_OLD/UPDATED_NEW etc. — even partial support is useful)
-- [ ] `ProjectionExpression` (return subset of attributes)
-- [ ] `FilterExpression` (post-query filter for Scan/Query)
-
-### 7) Test coverage / tooling
 - [ ] Add integration tests mirroring AWS CLI script flows:
   - create table → put → get → scan → query → delete
 - [ ] Add fuzz-ish tests for:
@@ -84,69 +59,20 @@ Goal: "aws cli works reliably for CreateTable/ListTables/PutItem/GetItem/DeleteI
   - expression parsing robustness
   - TLV decode failure cases (corrupt bytes)
 
----
+### 7) Secondary indexes
-
+- [x] Global Secondary Indexes (GSI)
-## Bug Fixes Applied This Session
-
-### Pagination (scan + query)
-**Bug**: `last_evaluated_key` was set to the key of the *next unread* item (the item at `count == limit`). When the client resumed with that key as `ExclusiveStartKey`, it would seek-then-skip, **dropping one item** from the result set.
-
-**Fix**: Now tracks the key of the *last successfully returned* item. Only emits `LastEvaluatedKey` when we confirm there are more items beyond the returned set (via `has_more` flag).
-
-### Sort key condition filtering
-**Bug**: `query()` performed a partition-prefix scan but never applied the sort key condition (=, <, BETWEEN, begins_with, etc.) from `KeyConditionExpression`. All items in the partition were returned regardless of sort key predicates.
-
-**Fix**: `query()` now accepts an optional `Sort_Key_Condition` parameter. The handler extracts it from the parsed `Key_Condition` and passes it through. `evaluate_sort_key_condition()` compares the item's SK attribute against the condition using string comparison (matching DynamoDB's lexicographic semantics for S/N/B keys).
-
-### Write locking
-**Bug**: `put_item` and `delete_item` acquired *shared* (read) locks. Multiple concurrent writes to the same table could interleave without mutual exclusion.
-
-**Fix**: Both now acquire *exclusive* (write) locks via `sync.rw_mutex_lock`. Read operations (`get_item`, `scan`, `query`) continue to use shared locks.
-
-### delete_table item cleanup
-**Bug**: `delete_table` only deleted the metadata key, leaving all data items orphaned in RocksDB.
-
-**Fix**: Before deleting metadata, `delete_table` now iterates over all keys with the table's data prefix and deletes them individually.
-
-### Item key type validation
-**New**: `put_item` now validates that the item's key attribute types match the table's `AttributeDefinitions`. E.g., if PK is declared as `S`, putting an item with a numeric PK is rejected with `Invalid_Key`.
-
-### Error response standardization
-**Fix**: Centralized all storage-error-to-HTTP-error mapping in `handle_storage_error`. InternalServerError maps to HTTP 500; all client errors (validation, not-found, etc.) map to HTTP 400. Missing `X-Amz-Target` now returns `SerializationException` to match real DynamoDB behavior.
-
----
-
-## Later (big features)
-These align with the "Future Enhancements" list in ARCHITECTURE.md.
-
-### 8) Secondary indexes
-- [ ] Global Secondary Indexes (GSI)
 - [ ] Local Secondary Indexes (LSI)
-- [ ] Index backfill + write-path maintenance
+- [ ] Index backfill (existing data when GSI added to populated table)
+- [x] Write-path maintenance (GSI)
 
-### 9) Batch + transactions
+### 8) Performance / ops
-- [ ] BatchWriteItem
-- [ ] BatchGetItem
-- [ ] Transactions (TransactWriteItems / TransactGetItems)
-
-### 10) Performance / ops
 - [ ] Connection reuse / keep-alive tuning
 - [ ] Bloom filters / RocksDB options tuning for common patterns
 - [ ] Optional compression policy (LZ4/Zstd knobs)
 - [ ] Parallel scan (segment scanning)
 
----
+### 9) Replication / WAL
-
-## Replication / WAL
 (There is a C++ shim stubbed out for WAL iteration and applying write batches.)
 - [ ] Implement WAL iterator: `latest_sequence`, `wal_iter_next` returning writebatch blob
 - [ ] Implement apply-writebatch on follower
 - [ ] Add a minimal replication test harness (leader generates N ops → follower applies → compare)
-
----
-
-## Housekeeping
-- [x] Fix TODO hygiene: keep this file short and "actionable"
-  - Added "Bug Fixes Applied" section documenting what changed and why
-- [ ] Add a CONTRIBUTING quick checklist (allocator rules, formatting, tests)
-- [ ] Add "known limitations" section in README (unsupported DynamoDB features)

dynamodb/batch.odin

@@ -0,0 +1,262 @@
+// BatchWriteItem and BatchGetItem storage operations
+//
+// BatchWriteItem: Puts or deletes multiple items across one or more tables.
+//   - Up to 25 items per batch (DynamoDB limit)
+//   - Each item is an independent PutRequest or DeleteRequest
+//   - Partial failures are reported via UnprocessedItems
+//
+// BatchGetItem: Retrieves multiple items from one or more tables.
+//   - Up to 100 items per batch (DynamoDB limit)
+//   - Each table request contains a list of Keys
+//   - Partial failures reported via UnprocessedKeys
+package dynamodb
+
+// ============================================================================
+// BatchWriteItem Types
+// ============================================================================
+
+Write_Request_Type :: enum {
+	Put,
+	Delete,
+}
+
+Write_Request :: struct {
+	type:  Write_Request_Type,
+	item:  Item,   // For Put: the full item.  For Delete: the key item.
+}
+
+Batch_Write_Table_Request :: struct {
+	table_name: string,
+	requests:   []Write_Request,
+}
+
+Batch_Write_Result :: struct {
+	// UnprocessedItems — requests that failed and should be retried.
+	// For now we process everything or return an error, so this is
+	// typically empty. Populated only on partial failures.
+	unprocessed: [dynamic]Batch_Write_Table_Request,
+}
+
+batch_write_result_destroy :: proc(result: ^Batch_Write_Result) {
+	for &table_req in result.unprocessed {
+		for &req in table_req.requests {
+			item_destroy(&req.item)
+		}
+		delete(table_req.requests)
+	}
+	delete(result.unprocessed)
+}
+
+// ============================================================================
+// BatchWriteItem — Execute a batch of put/delete operations
+//
+// DynamoDB semantics:
+//   - Operations within a batch are NOT atomic (some may succeed, some fail)
+//   - Each operation is validated independently
+//   - Failed operations go into UnprocessedItems
+//   - Limit: 25 operations total across all tables
+// ============================================================================
+
+batch_write_item :: proc(
+	engine: ^Storage_Engine,
+	table_requests: []Batch_Write_Table_Request,
+) -> (Batch_Write_Result, Storage_Error) {
+	result := Batch_Write_Result{
+		unprocessed = make([dynamic]Batch_Write_Table_Request),
+	}
+
+	// Count total operations across all tables
+	total_ops := 0
+	for table_req in table_requests {
+		total_ops += len(table_req.requests)
+	}
+
+	// Enforce DynamoDB limit: 25 operations per batch
+	if total_ops > 25 {
+		return result, .Validation_Error
+	}
+
+	for table_req in table_requests {
+		failed_requests := make([dynamic]Write_Request)
+
+		for req in table_req.requests {
+			var_err: Storage_Error
+
+			switch req.type {
+			case .Put:
+				var_err = put_item(engine, table_req.table_name, req.item)
+			case .Delete:
+				var_err = delete_item(engine, table_req.table_name, req.item)
+			}
+
+			// Distinguish validation errors from transient failures
+			if var_err != .None {
+				#partial switch var_err {
+				case .Missing_Key_Attribute, .Invalid_Key, .Serialization_Error:
+					// Hard validation errors — fail the entire batch
+					batch_write_result_destroy(&result)
+					delete(failed_requests)
+					return result, var_err
+
+				case .Table_Not_Found:
+					// Non-existent table is a hard request failure, not a retryable condition.
+					// DynamoDB returns ResourceNotFoundException for the whole request.
+					batch_write_result_destroy(&result)
+					delete(failed_requests)
+					return result, .Table_Not_Found
+
+				case .RocksDB_Error, .Item_Not_Found:
+					// Genuinely transient/infrastructure errors — add to UnprocessedItems.
+					failed_item := item_deep_copy(req.item)
+					append(&failed_requests, Write_Request{
+						type = req.type,
+						item = failed_item,
+					})
+
+				case .None, .Validation_Error, .Internal_Error:
+					// Should not happen, but handle gracefully
+					failed_item := item_deep_copy(req.item)
+					append(&failed_requests, Write_Request{
+						type = req.type,
+						item = failed_item,
+					})
+				}
+			}
+		}
+
+		if len(failed_requests) > 0 {
+			append(&result.unprocessed, Batch_Write_Table_Request{
+				table_name = table_req.table_name,
+				requests   = failed_requests[:],
+			})
+		} else {
+			delete(failed_requests)
+		}
+	}
+
+	return result, .None
+}
+
+
+// ============================================================================
+// BatchGetItem Types
+// ============================================================================
+
+Batch_Get_Table_Request :: struct {
+	table_name: string,
+	keys:       []Item,
+}
+
+Batch_Get_Table_Result :: struct {
+	table_name: string,
+	items:      []Item,
+}
+
+Batch_Get_Result :: struct {
+	responses:       [dynamic]Batch_Get_Table_Result,
+	unprocessed_keys: [dynamic]Batch_Get_Table_Request,
+}
+
+batch_get_result_destroy :: proc(result: ^Batch_Get_Result) {
+	for &table_result in result.responses {
+		for &item in table_result.items {
+			item_destroy(&item)
+		}
+		delete(table_result.items)
+	}
+	delete(result.responses)
+
+	for &table_req in result.unprocessed_keys {
+		for &key in table_req.keys {
+			item_destroy(&key)
+		}
+		delete(table_req.keys)
+	}
+	delete(result.unprocessed_keys)
+}
+
+// ============================================================================
+// BatchGetItem — Retrieve multiple items from one or more tables
+//
+// DynamoDB semantics:
+//   - Each key is fetched independently
+//   - Missing items are silently omitted (no error)
+//   - Failed lookups go into UnprocessedKeys
+//   - Limit: 100 keys total across all tables
+// ============================================================================
+
+batch_get_item :: proc(
+	engine: ^Storage_Engine,
+	table_requests: []Batch_Get_Table_Request,
+) -> (Batch_Get_Result, Storage_Error) {
+	result := Batch_Get_Result{
+		responses        = make([dynamic]Batch_Get_Table_Result),
+		unprocessed_keys = make([dynamic]Batch_Get_Table_Request),
+	}
+
+	// Count total keys across all tables
+	total_keys := 0
+	for table_req in table_requests {
+		total_keys += len(table_req.keys)
+	}
+
+	// Enforce DynamoDB limit: 100 keys per batch
+	if total_keys > 100 {
+		return result, .Validation_Error
+	}
+
+	for table_req in table_requests {
+		found_items := make([dynamic]Item)
+		failed_keys := make([dynamic]Item)
+
+		for key in table_req.keys {
+			item_result, get_err := get_item(engine, table_req.table_name, key)
+
+			// Distinguish validation errors from transient failures
+			if get_err != .None && get_err != .Item_Not_Found {
+				#partial switch get_err {
+				case .Missing_Key_Attribute, .Invalid_Key, .Serialization_Error:
+					// Hard validation error — fail the entire batch
+					batch_get_result_destroy(&result)
+					delete(found_items)
+					delete(failed_keys)
+					return result, get_err
+
+				case .RocksDB_Error, .Table_Not_Found:
+					// Transient error — add to unprocessed
+					append(&failed_keys, item_deep_copy(key))
+					continue
+
+				case .None, .Validation_Error, .Internal_Error, .Item_Not_Found:
+					// Should not happen here, but handle gracefully
+					continue
+				}
+			}
+
+			if item_val, has_item := item_result.?; has_item {
+				append(&found_items, item_val)
+			}
+			// If item not found, silently omit (DynamoDB behavior)
+		}
+
+		if len(found_items) > 0 {
+			append(&result.responses, Batch_Get_Table_Result{
+				table_name = table_req.table_name,
+				items      = found_items[:],
+			})
+		} else {
+			delete(found_items)
+		}
+
+		if len(failed_keys) > 0 {
+			append(&result.unprocessed_keys, Batch_Get_Table_Request{
+				table_name = table_req.table_name,
+				keys       = failed_keys[:],
+			})
+		} else {
+			delete(failed_keys)
+		}
+	}
+
+	return result, .None
+}

dynamodb/condition.odin

@@ -0,0 +1,119 @@
+// ConditionExpression support for PutItem, DeleteItem, and UpdateItem
+//
+// ConditionExpression uses the same grammar as FilterExpression but is evaluated
+// against the *existing* item (before the mutation). If the condition evaluates
+// to false, the operation is rejected with ConditionalCheckFailedException.
+//
+// When there is no existing item:
+//   - attribute_not_exists(path) → true  (attribute doesn't exist on a non-existent item)
+//   - attribute_exists(path)     → false
+//   - All comparisons            → false (no attribute to compare)
+//
+// This file provides:
+//   1. parse_condition_expression_string  — extract ConditionExpression from JSON body
+//   2. evaluate_condition                 — evaluate parsed condition against an item
+//   3. Condition_Result                   — result enum for condition evaluation
+package dynamodb
+
+import "core:encoding/json"
+import "core:strings"
+
+// ============================================================================
+// Condition Evaluation Result
+// ============================================================================
+
+Condition_Result :: enum {
+	Passed,              // Condition met (or no condition specified)
+	Failed,              // Condition not met → ConditionalCheckFailedException
+	Parse_Error,         // Malformed ConditionExpression → ValidationException
+}
+
+// ============================================================================
+// Request Parsing
+// ============================================================================
+
+// Extract the raw ConditionExpression string from the request body.
+parse_condition_expression_string :: proc(request_body: []byte) -> (expr: string, ok: bool) {
+	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
+	if parse_err != nil {
+		return
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		return
+	}
+
+	ce_val, found := root["ConditionExpression"]
+	if !found {
+		return
+	}
+
+	ce_str, str_ok := ce_val.(json.String)
+	if !str_ok {
+		return
+	}
+
+	expr = strings.clone(string(ce_str))
+	ok = true
+	return
+}
+
+// ============================================================================
+// Full Condition Evaluation Pipeline
+//
+// Parses ConditionExpression + ExpressionAttributeNames/Values from the
+// request body, then evaluates against the existing item.
+//
+// Parameters:
+//   request_body  — full JSON request body
+//   existing_item — the item currently in the database (nil if no item exists)
+//   attr_names    — pre-parsed ExpressionAttributeNames (caller may already have these)
+//   attr_values   — pre-parsed ExpressionAttributeValues
+//
+// Returns Condition_Result:
+//   .Passed      — no ConditionExpression, or condition evaluated to true
+//   .Failed      — condition evaluated to false
+//   .Parse_Error — ConditionExpression is malformed
+// ============================================================================
+
+evaluate_condition_expression :: proc(
+	request_body: []byte,
+	existing_item: Maybe(Item),
+	attr_names: Maybe(map[string]string),
+	attr_values: map[string]Attribute_Value,
+) -> Condition_Result {
+	// Extract ConditionExpression string
+	condition_str, has_condition := parse_condition_expression_string(request_body)
+	if !has_condition {
+		return .Passed // No condition → always pass
+	}
+	defer delete(condition_str)
+
+	// Parse the condition into a filter tree (same grammar as FilterExpression)
+	filter_node, parse_ok := parse_filter_expression(condition_str, attr_names, attr_values)
+	if !parse_ok || filter_node == nil {
+		return .Parse_Error
+	}
+	defer {
+		filter_node_destroy(filter_node)
+	}
+
+	// If there is no existing item, build an empty item for evaluation.
+	// This means attribute_not_exists → true, attribute_exists → false,
+	// all comparisons → false (attribute not found).
+	eval_item: Item
+	if item, has_item := existing_item.?; has_item {
+		eval_item = item
+	} else {
+		// Empty item — no attributes exist
+		eval_item = Item{}
+	}
+
+	if evaluate_filter(eval_item, filter_node) {
+		return .Passed
+	}
+
+	return .Failed
+}

dynamodb/expression.odin

@@ -32,6 +32,7 @@ Sort_Key_Condition :: struct {
 }
 
 sort_key_condition_destroy :: proc(skc: ^Sort_Key_Condition) {
+	delete(skc.sk_name)  // Free the cloned string
 	attr_value_destroy(&skc.value)
 	if v2, ok := skc.value2.?; ok {
 		v2_copy := v2
@@ -46,6 +47,7 @@ Key_Condition :: struct {
 }
 
 key_condition_destroy :: proc(kc: ^Key_Condition) {
+	delete(kc.pk_name)  // Free the cloned string
 	attr_value_destroy(&kc.pk_value)
 	if skc, ok := kc.sk_condition.?; ok {
 		skc_copy := skc
@@ -58,8 +60,9 @@ key_condition_get_pk_bytes :: proc(kc: ^Key_Condition) -> ([]byte, bool) {
 	#partial switch v in kc.pk_value {
 	case String:
 		return transmute([]byte)string(v), true
-	case Number:
+	case DDB_Number:
-		return transmute([]byte)string(v), true
+		// Use canonical encoding for numbers in keys!
+		return encode_ddb_number_for_sort(v), true
 	case Binary:
 		return transmute([]byte)string(v), true
 	}
@@ -108,7 +111,7 @@ tokenizer_next :: proc(t: ^Tokenizer) -> Maybe(string) {
 	}
 
 	// Single-character operators
-	if c == '=' || c == '<' || c == '>' {
+	if c == '=' || c == '<' || c == '>' || c == '+' || c == '-' {
 		t.pos += 1
 		return t.input[start:t.pos]
 	}
@@ -135,16 +138,16 @@ is_whitespace :: proc(c: byte) -> bool {
 @(private = "file")
 is_ident_char :: proc(c: byte) -> bool {
 	return (c >= 'a' && c <= 'z') ||
-	       (c >= 'A' && c <= 'Z') ||
+			(c >= 'A' && c <= 'Z') ||
-	       (c >= '0' && c <= '9') ||
+			(c >= '0' && c <= '9') ||
-	       c == '_' || c == ':' || c == '#' || c == '-' || c == '.'
+			c == '_' || c == ':' || c == '#' || c == '.'
 }
 
 // ---------------------------------------------------------------------------
 // Helper: convert Maybe(string) tokens into (string, bool) so or_return works.
 // ---------------------------------------------------------------------------
 
-@(private = "file")
+// Package-visible: used by update.odin and filter.odin
 next_token :: proc(t: ^Tokenizer) -> (tok: string, ok: bool) {
 	if v, has := tokenizer_next(t).?; has {
 		tok = v
@@ -166,16 +169,19 @@ parse_key_condition_expression :: proc(
 	t := tokenizer_init(expression)
 
 	pk_name_token := next_token(&t) or_return
-	pk_name       := resolve_attribute_name(pk_name_token, attribute_names) or_return
+	pk_name_unowned := resolve_attribute_name(pk_name_token, attribute_names) or_return
+	pk_name := strings.clone(pk_name_unowned)  // Clone for safe storage
 
 	eq_token := next_token(&t) or_return
 	if eq_token != "=" {
+		delete(pk_name) // free on error
 		return
 	}
 
 	pk_value_token := next_token(&t) or_return
 	pk_value, pk_ok := resolve_attribute_value(pk_value_token, attribute_values)
 	if !pk_ok {
+		delete(pk_name) // free on error
 		return
 	}
 
@@ -184,18 +190,30 @@ parse_key_condition_expression :: proc(
 	// Optional "AND ..."
 	if and_token, has_and := tokenizer_next(&t).?; has_and {
 		if !strings.equal_fold(and_token, "AND") {
+			delete(pk_name) // free on error
 			attr_value_destroy(&pk_value)
 			return
 		}
 
 		skc, skc_ok := parse_sort_key_condition(&t, attribute_names, attribute_values)
 		if !skc_ok {
+			delete(pk_name) // free on error
 			attr_value_destroy(&pk_value)
 			return
 		}
 		sk_condition = skc
 	}
 
+	// Verify all tokens were consumed (no trailing garbage)
+	if trailing := tokenizer_next(&t); trailing != nil {
+		delete(pk_name)
+		attr_value_destroy(&pk_value)
+		if skc, has_skc := sk_condition.?; has_skc {
+			skc_copy := skc
+			sort_key_condition_destroy(&skc_copy)
+		}
+		return
+	}
 
 	kc = Key_Condition{
 		pk_name      = pk_name,
@@ -219,17 +237,20 @@ parse_sort_key_condition :: proc(
 		return
 	}
 
-	sk_name := resolve_attribute_name(first_token, attribute_names) or_return
+	sk_name_unowned := resolve_attribute_name(first_token, attribute_names) or_return
+	sk_name := strings.clone(sk_name_unowned)  // Clone for safe storage
 
 	op_token := next_token(t) or_return
 	operator, op_ok := parse_operator(op_token)
 	if !op_ok {
+		delete(sk_name)  // free on error
 		return
 	}
 
 	value_token := next_token(t) or_return
 	value, val_ok := resolve_attribute_value(value_token, attribute_values)
 	if !val_ok {
+		delete(sk_name)  // free on error
 		return
 	}
 
@@ -238,18 +259,21 @@ parse_sort_key_condition :: proc(
 		// IMPORTANT: after allocating `value`, do NOT use `or_return` without cleanup.
 		and_token, tok_ok := next_token(t)
 		if !tok_ok || !strings.equal_fold(and_token, "AND") {
+			delete(sk_name)  // free on error
 			attr_value_destroy(&value)
 			return
 		}
 
 		value2_token, tok2_ok := next_token(t)
 		if !tok2_ok {
+			delete(sk_name)  // free on error
 			attr_value_destroy(&value)
 			return
 		}
 
 		v2, v2_ok := resolve_attribute_value(value2_token, attribute_values)
 		if !v2_ok {
+			delete(sk_name)  // free on error
 			attr_value_destroy(&value)
 			return
 		}
@@ -278,22 +302,26 @@ parse_begins_with :: proc(
 	}
 
 	sk_name_token := next_token(t) or_return
-	sk_name       := resolve_attribute_name(sk_name_token, attribute_names) or_return
+	sk_name_unowned := resolve_attribute_name(sk_name_token, attribute_names) or_return
+	sk_name := strings.clone(sk_name_unowned)  // Clone for safe storage
 
 	comma := next_token(t) or_return
 	if comma != "," {
+		delete(sk_name)  // free on error
 		return
 	}
 
 	value_token := next_token(t) or_return
 	value, val_ok := resolve_attribute_value(value_token, attribute_values)
 	if !val_ok {
+		delete(sk_name)  // free on error
 		return
 	}
 
 	// after allocating `value`, avoid `or_return` so we can clean up
 	rparen, tok_ok := next_token(t)
 	if !tok_ok || rparen != ")" {
+		delete(sk_name)  // free on error
 		attr_value_destroy(&value)
 		return
 	}
@@ -319,7 +347,7 @@ parse_operator :: proc(token: string) -> (Sort_Key_Operator, bool) {
 	return .EQ, false
 }
 
-@(private = "file")
+// Package-visible: used by update.odin and filter.odin
 resolve_attribute_name :: proc(token: string, names: Maybe(map[string]string)) -> (string, bool) {
 	if len(token) > 0 && token[0] == '#' {
 		if n, has_names := names.?; has_names {
@@ -332,7 +360,7 @@ resolve_attribute_name :: proc(token: string, names: Maybe(map[string]string)) -
 	return token, true
 }
 
-@(private = "file")
+// Package-visible: used by update.odin and filter.odin
 resolve_attribute_value :: proc(
 	token: string,
 	values: map[string]Attribute_Value,
@@ -388,13 +416,13 @@ parse_expression_attribute_names :: proc(request_body: []byte) -> Maybe(map[stri
 parse_expression_attribute_values :: proc(request_body: []byte) -> (map[string]Attribute_Value, bool) {
 	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
 	if parse_err != nil {
-		return make(map[string]Attribute_Value), true
+		return make(map[string]Attribute_Value), false
 	}
 	defer json.destroy_value(data)
 
 	root, ok := data.(json.Object)
 	if !ok {
-		return make(map[string]Attribute_Value), true
+		return make(map[string]Attribute_Value), false
 	}
 
 	values_val, found := root["ExpressionAttributeValues"]
@@ -404,7 +432,7 @@ parse_expression_attribute_values :: proc(request_body: []byte) -> (map[string]A
 
 	values_obj, values_ok := values_val.(json.Object)
 	if !values_ok {
-		return make(map[string]Attribute_Value), true
+		return make(map[string]Attribute_Value), false
 	}
 
 	result := make(map[string]Attribute_Value)
@@ -412,7 +440,13 @@ parse_expression_attribute_values :: proc(request_body: []byte) -> (map[string]A
 	for key, val in values_obj {
 		attr, attr_ok := parse_attribute_value(val)
 		if !attr_ok {
-			continue
+			// Clean up already-parsed values before returning error
+			for k, &v in result {
+				attr_value_destroy(&v)
+				delete(k)
+			}
+			delete(result)
+			return make(map[string]Attribute_Value), false
 		}
 		result[strings.clone(key)] = attr
 	}
@@ -446,7 +480,7 @@ parse_key_condition_expression_string :: proc(request_body: []byte) -> (expr: st
 		return
 	}
 
-	expr = string(kce_str)
+	expr = strings.clone(string(kce_str))
 	ok = true
 	return
 }
@@ -454,6 +488,7 @@ parse_key_condition_expression_string :: proc(request_body: []byte) -> (expr: st
 // Convenience: parse a complete Query key condition from request body
 parse_query_key_condition :: proc(request_body: []byte) -> (kc: Key_Condition, ok: bool) {
 	expression := parse_key_condition_expression_string(request_body) or_return
+	defer delete(expression)
 
 	attr_names := parse_expression_attribute_names(request_body)
 	defer {

dynamodb/filter.odin

@@ -0,0 +1,833 @@
+// FilterExpression and ProjectionExpression support
+// FilterExpression:    post-retrieval filter applied to Scan/Query results
+// ProjectionExpression: return only specified attributes from items
+package dynamodb
+
+import "core:encoding/json"
+import "core:strings"
+import "core:mem"
+
+// ============================================================================
+// ProjectionExpression
+//
+// A comma-separated list of attribute names (with optional #name substitution)
+// that specifies which attributes to return.
+// ============================================================================
+
+parse_projection_expression :: proc(
+	request_body: []byte,
+	attribute_names: Maybe(map[string]string),
+) -> (paths: []string, ok: bool) {
+	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
+	if parse_err != nil {
+		return nil, false
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		return nil, false
+	}
+
+	pe_val, found := root["ProjectionExpression"]
+	if !found {
+		return nil, false // absent is not an error, caller should check
+	}
+
+	pe_str, str_ok := pe_val.(json.String)
+	if !str_ok {
+		return nil, false
+	}
+
+	// Split by comma and resolve names
+	parts := strings.split(string(pe_str), ",")
+	result := make([dynamic]string)
+
+	for part in parts {
+		trimmed := strings.trim_space(part)
+		if len(trimmed) == 0 {
+			continue
+		}
+
+		resolved, res_ok := resolve_attribute_name(trimmed, attribute_names)
+		if !res_ok {
+			// Cleanup previously cloned strings
+			for path in result {
+				delete(path)
+			}
+			delete(result)
+			return nil, false
+		}
+		append(&result, strings.clone(resolved))  // Clone for safe storage
+	}
+
+	return result[:], true
+}
+
+// Apply projection to a single item — returns a new item with only the specified attributes
+apply_projection :: proc(item: Item, projection: []string) -> Item {
+	if len(projection) == 0 {
+		// No projection — return a deep copy of the full item
+		return item_deep_copy(item)
+	}
+
+	projected := make(Item)
+	for path in projection {
+		if val, found := item[path]; found {
+			projected[strings.clone(path)] = attr_value_deep_copy(val)
+		}
+	}
+	return projected
+}
+
+// Deep copy an entire item
+item_deep_copy :: proc(item: Item) -> Item {
+	result := make(Item)
+	for key, val in item {
+		result[strings.clone(key)] = attr_value_deep_copy(val)
+	}
+	return result
+}
+
+// ============================================================================
+// FilterExpression
+//
+// A condition expression applied post-retrieval. Supports:
+//   - Comparisons:  path = :val,  path <> :val,  path < :val, etc.
+//   - BETWEEN:      path BETWEEN :lo AND :hi
+//   - IN:           path IN (:v1, :v2, :v3)
+//   - begins_with:  begins_with(path, :prefix)
+//   - contains:     contains(path, :substr)
+//   - attribute_exists(path)
+//   - attribute_not_exists(path)
+//   - AND / OR / NOT combinators
+//
+// This is a recursive-descent parser for condition expressions.
+// ============================================================================
+
+// Parsed filter node (expression tree)
+Filter_Node_Type :: enum {
+	Comparison,        // path op value
+	Between,           // path BETWEEN lo AND hi
+	In,                // path IN (v1, v2, ...)
+	Begins_With,       // begins_with(path, value)
+	Contains,          // contains(path, value)
+	Attribute_Exists,  // attribute_exists(path)
+	Attribute_Not_Exists, // attribute_not_exists(path)
+	And,               // left AND right
+	Or,                // left OR right
+	Not,               // NOT child
+}
+
+Comparison_Op :: enum {
+	EQ,  // =
+	NE,  // <>
+	LT,  // <
+	LE,  // <=
+	GT,  // >
+	GE,  // >=
+}
+
+Filter_Node :: struct {
+	type:     Filter_Node_Type,
+	// For Comparison
+	path:     string,
+	comp_op:  Comparison_Op,
+	value:    Attribute_Value,
+	// For Between
+	value2:   Maybe(Attribute_Value),
+	// For In
+	in_values: []Attribute_Value,
+	// For And/Or
+	left:     ^Filter_Node,
+	right:    ^Filter_Node,
+	// For Not
+	child:    ^Filter_Node,
+	allocator: mem.Allocator, // allocator that created this node
+}
+
+filter_node_destroy :: proc(node: ^Filter_Node) {
+	if node == nil {
+		return
+	}
+
+	attr_value_destroy(&node.value)
+	if v2, ok := node.value2.?; ok {
+		v2_copy := v2
+		attr_value_destroy(&v2_copy)
+	}
+	for &iv in node.in_values {
+		attr_value_destroy(&iv)
+	}
+	if node.in_values != nil {
+		delete(node.in_values)
+	}
+
+	if node.left != nil {
+		filter_node_destroy(node.left)
+	}
+	if node.right != nil {
+		filter_node_destroy(node.right)
+	}
+	if node.child != nil {
+		filter_node_destroy(node.child)
+	}
+
+	// Free the node itself using the allocator that created it
+	free(node, node.allocator)
+}
+
+// ============================================================================
+// Filter Expression Parser
+// ============================================================================
+
+parse_filter_expression :: proc(
+	expression: string,
+	attribute_names: Maybe(map[string]string),
+	attribute_values: map[string]Attribute_Value,
+) -> (node: ^Filter_Node, ok: bool) {
+	t := tokenizer_init(expression)
+	node, ok = parse_or_expr(&t, attribute_names, attribute_values)
+	if !ok {
+		return nil, false
+	}
+
+	// Verify all tokens were consumed (no trailing garbage)
+	if trailing := tokenizer_next(&t); trailing != nil {
+		filter_node_destroy(node)
+		return nil, false
+	}
+
+	return node, true
+}
+
+parse_or_expr :: proc(
+	t: ^Tokenizer,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	left, left_ok := parse_and_expr(t, names, values)
+	if !left_ok {
+		return nil, false
+	}
+
+	for {
+		saved_pos := t.pos
+		tok_maybe := tokenizer_next(t)
+		tok, has := tok_maybe.?
+		if !has {
+			break
+		}
+
+		if strings.equal_fold(tok, "OR") {
+			right, right_ok := parse_and_expr(t, names, values)
+			if !right_ok {
+				filter_node_destroy(left)
+				return nil, false
+			}
+
+			parent := make_filter_node()
+			parent.type = .Or
+			parent.left = left
+			parent.right = right
+			left = parent
+		} else {
+			t.pos = saved_pos
+			break
+		}
+	}
+
+	return left, true
+}
+
+parse_and_expr :: proc(
+	t: ^Tokenizer,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	left, left_ok := parse_not_expr(t, names, values)
+	if !left_ok {
+		return nil, false
+	}
+
+	for {
+		saved_pos := t.pos
+		tok_maybe := tokenizer_next(t)
+		tok, has := tok_maybe.?
+		if !has {
+			break
+		}
+
+		if strings.equal_fold(tok, "AND") {
+			right, right_ok := parse_not_expr(t, names, values)
+			if !right_ok {
+				filter_node_destroy(left)
+				return nil, false
+			}
+
+			parent := make_filter_node()
+			parent.type = .And
+			parent.left = left
+			parent.right = right
+			left = parent
+		} else {
+			t.pos = saved_pos
+			break
+		}
+	}
+
+	return left, true
+}
+
+parse_not_expr :: proc(
+	t: ^Tokenizer,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	saved_pos := t.pos
+	tok_maybe := tokenizer_next(t)
+	tok, has := tok_maybe.?
+	if !has {
+		return nil, false
+	}
+
+	if strings.equal_fold(tok, "NOT") {
+		child, child_ok := parse_primary_expr(t, names, values)
+		if !child_ok {
+			return nil, false
+		}
+		node := make_filter_node()
+		node.type = .Not
+		node.child = child
+		return node, true
+	}
+
+	t.pos = saved_pos
+	return parse_primary_expr(t, names, values)
+}
+
+parse_primary_expr :: proc(
+	t: ^Tokenizer,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	first_tok, first_ok := next_token(t)
+	if !first_ok {
+		return nil, false
+	}
+
+	// Parenthesized expression
+	if first_tok == "(" {
+		inner, inner_ok := parse_or_expr(t, names, values)
+		if !inner_ok {
+			return nil, false
+		}
+		rparen, rp_ok := next_token(t)
+		if !rp_ok || rparen != ")" {
+			filter_node_destroy(inner)
+			return nil, false
+		}
+		return inner, true
+	}
+
+	// Function-style: begins_with, contains, attribute_exists, attribute_not_exists
+	if strings.equal_fold(first_tok, "begins_with") {
+		return parse_filter_begins_with(t, names, values)
+	}
+	if strings.equal_fold(first_tok, "contains") {
+		return parse_filter_contains(t, names, values)
+	}
+	if strings.equal_fold(first_tok, "attribute_exists") {
+		return parse_filter_attr_exists(t, names, true)
+	}
+	if strings.equal_fold(first_tok, "attribute_not_exists") {
+		return parse_filter_attr_exists(t, names, false)
+	}
+
+	// Comparison, BETWEEN, or IN: path op value
+	path, path_ok := resolve_attribute_name(first_tok, names)
+	if !path_ok {
+		return nil, false
+	}
+
+	op_tok, op_ok := next_token(t)
+	if !op_ok {
+		return nil, false
+	}
+
+	// BETWEEN
+	if strings.equal_fold(op_tok, "BETWEEN") {
+		return parse_filter_between(t, path, names, values)
+	}
+
+	// IN
+	if strings.equal_fold(op_tok, "IN") {
+		return parse_filter_in(t, path, names, values)
+	}
+
+	// Comparison operators
+	comp_op: Comparison_Op
+	if op_tok == "=" {
+		comp_op = .EQ
+	} else if op_tok == "<>" {
+		comp_op = .NE
+	} else if op_tok == "<" {
+		comp_op = .LT
+	} else if op_tok == "<=" {
+		comp_op = .LE
+	} else if op_tok == ">" {
+		comp_op = .GT
+	} else if op_tok == ">=" {
+		comp_op = .GE
+	} else {
+		return nil, false
+	}
+
+	val_tok, vt_ok := next_token(t)
+	if !vt_ok {
+		return nil, false
+	}
+	val, val_ok := resolve_attribute_value(val_tok, values)
+	if !val_ok {
+		return nil, false
+	}
+
+	node := make_filter_node()
+	node.type = .Comparison
+	node.path = path
+	node.comp_op = comp_op
+	node.value = val
+	return node, true
+}
+
+parse_filter_begins_with :: proc(
+	t: ^Tokenizer,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	lparen, lp_ok := next_token(t)
+	if !lp_ok || lparen != "(" {
+		return nil, false
+	}
+
+	path_tok, path_ok := next_token(t)
+	if !path_ok {
+		return nil, false
+	}
+	path, path_resolved := resolve_attribute_name(path_tok, names)
+	if !path_resolved {
+		return nil, false
+	}
+
+	comma, comma_ok := next_token(t)
+	if !comma_ok || comma != "," {
+		return nil, false
+	}
+
+	val_tok, vt_ok := next_token(t)
+	if !vt_ok {
+		return nil, false
+	}
+	val, val_ok := resolve_attribute_value(val_tok, values)
+	if !val_ok {
+		return nil, false
+	}
+
+	rparen, rp_ok := next_token(t)
+	if !rp_ok || rparen != ")" {
+		attr_value_destroy(&val)
+		return nil, false
+	}
+
+	node := make_filter_node()
+	node.type = .Begins_With
+	node.path = path
+	node.value = val
+	return node, true
+}
+
+parse_filter_contains :: proc(
+	t: ^Tokenizer,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	lparen, lp_ok := next_token(t)
+	if !lp_ok || lparen != "(" {
+		return nil, false
+	}
+
+	path_tok, path_ok := next_token(t)
+	if !path_ok {
+		return nil, false
+	}
+	path, path_resolved := resolve_attribute_name(path_tok, names)
+	if !path_resolved {
+		return nil, false
+	}
+
+	comma, comma_ok := next_token(t)
+	if !comma_ok || comma != "," {
+		return nil, false
+	}
+
+	val_tok, vt_ok := next_token(t)
+	if !vt_ok {
+		return nil, false
+	}
+	val, val_ok := resolve_attribute_value(val_tok, values)
+	if !val_ok {
+		return nil, false
+	}
+
+	rparen, rp_ok := next_token(t)
+	if !rp_ok || rparen != ")" {
+		attr_value_destroy(&val)
+		return nil, false
+	}
+
+	node := make_filter_node()
+	node.type = .Contains
+	node.path = path
+	node.value = val
+	return node, true
+}
+
+parse_filter_attr_exists :: proc(
+	t: ^Tokenizer,
+	names: Maybe(map[string]string),
+	exists: bool,
+) -> (^Filter_Node, bool) {
+	lparen, lp_ok := next_token(t)
+	if !lp_ok || lparen != "(" {
+		return nil, false
+	}
+
+	path_tok, path_ok := next_token(t)
+	if !path_ok {
+		return nil, false
+	}
+	path, path_resolved := resolve_attribute_name(path_tok, names)
+	if !path_resolved {
+		return nil, false
+	}
+
+	rparen, rp_ok := next_token(t)
+	if !rp_ok || rparen != ")" {
+		return nil, false
+	}
+
+	node := make_filter_node()
+	node.type = .Attribute_Exists if exists else .Attribute_Not_Exists
+	node.path = path
+	return node, true
+}
+
+parse_filter_between :: proc(
+	t: ^Tokenizer,
+	path: string,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	lo_tok, lo_ok := next_token(t)
+	if !lo_ok {
+		return nil, false
+	}
+	lo_val, lo_val_ok := resolve_attribute_value(lo_tok, values)
+	if !lo_val_ok {
+		return nil, false
+	}
+
+	and_tok, and_ok := next_token(t)
+	if !and_ok || !strings.equal_fold(and_tok, "AND") {
+		attr_value_destroy(&lo_val)
+		return nil, false
+	}
+
+	hi_tok, hi_ok := next_token(t)
+	if !hi_ok {
+		attr_value_destroy(&lo_val)
+		return nil, false
+	}
+	hi_val, hi_val_ok := resolve_attribute_value(hi_tok, values)
+	if !hi_val_ok {
+		attr_value_destroy(&lo_val)
+		return nil, false
+	}
+
+	node := make_filter_node()
+	node.type = .Between
+	node.path = path
+	node.value = lo_val
+	node.value2 = hi_val
+	return node, true
+}
+
+parse_filter_in :: proc(
+	t: ^Tokenizer,
+	path: string,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (^Filter_Node, bool) {
+	lparen, lp_ok := next_token(t)
+	if !lp_ok || lparen != "(" {
+		return nil, false
+	}
+
+	in_vals := make([dynamic]Attribute_Value)
+
+	for {
+		val_tok, vt_ok := next_token(t)
+		if !vt_ok {
+			for &v in in_vals {
+				attr_value_destroy(&v)
+			}
+			delete(in_vals)
+			return nil, false
+		}
+
+		val, val_ok := resolve_attribute_value(val_tok, values)
+		if !val_ok {
+			for &v in in_vals {
+				attr_value_destroy(&v)
+			}
+			delete(in_vals)
+			return nil, false
+		}
+		append(&in_vals, val)
+
+		sep_tok, sep_ok := next_token(t)
+		if !sep_ok {
+			for &v in in_vals {
+				attr_value_destroy(&v)
+			}
+			delete(in_vals)
+			return nil, false
+		}
+		if sep_tok == ")" {
+			break
+		}
+		if sep_tok != "," {
+			for &v in in_vals {
+				attr_value_destroy(&v)
+			}
+			delete(in_vals)
+			return nil, false
+		}
+	}
+
+	node := make_filter_node()
+	node.type = .In
+	node.path = path
+	node.in_values = in_vals[:]
+	return node, true
+}
+
+// ============================================================================
+// Filter Expression Evaluation
+// ============================================================================
+
+evaluate_filter :: proc(item: Item, node: ^Filter_Node) -> bool {
+	if node == nil {
+		return true
+	}
+
+	switch node.type {
+	case .Comparison:
+		attr, found := item[node.path]
+		if !found {
+			return false
+		}
+		return evaluate_comparison(attr, node.comp_op, node.value)
+
+	case .Between:
+		attr, found := item[node.path]
+		if !found {
+			return false
+		}
+		lo_cmp := compare_attribute_values(attr, node.value)
+		if v2, ok := node.value2.?; ok {
+			hi_cmp := compare_attribute_values(attr, v2)
+			return lo_cmp >= 0 && hi_cmp <= 0
+		}
+		return false
+
+	case .In:
+		attr, found := item[node.path]
+		if !found {
+			return false
+		}
+		for in_val in node.in_values {
+			if compare_attribute_values(attr, in_val) == 0 {
+				return true
+			}
+		}
+		return false
+
+	case .Begins_With:
+		attr, found := item[node.path]
+		if !found {
+			return false
+		}
+		attr_str, attr_ok := attr_value_to_string_for_compare(attr)
+		val_str, val_ok := attr_value_to_string_for_compare(node.value)
+		if !attr_ok || !val_ok {
+			return false
+		}
+		return strings.has_prefix(attr_str, val_str)
+
+	case .Contains:
+		attr, found := item[node.path]
+		if !found {
+			return false
+		}
+		return evaluate_contains(attr, node.value)
+
+	case .Attribute_Exists:
+		_, found := item[node.path]
+		return found
+
+	case .Attribute_Not_Exists:
+		_, found := item[node.path]
+		return !found
+
+	case .And:
+		return evaluate_filter(item, node.left) && evaluate_filter(item, node.right)
+
+	case .Or:
+		return evaluate_filter(item, node.left) || evaluate_filter(item, node.right)
+
+	case .Not:
+		return !evaluate_filter(item, node.child)
+	}
+
+	return false
+}
+
+evaluate_comparison :: proc(attr: Attribute_Value, op: Comparison_Op, val: Attribute_Value) -> bool {
+	cmp := compare_attribute_values(attr, val)
+
+	// -2 means types are incomparable - all comparisons return false
+	// (matches DynamoDB behavior: mixed-type comparisons always fail)
+	if cmp == -2 {
+		return false
+	}
+
+	switch op {
+	case .EQ: return cmp == 0
+	case .NE: return cmp != 0
+	case .LT: return cmp < 0
+	case .LE: return cmp <= 0
+	case .GT: return cmp > 0
+	case .GE: return cmp >= 0
+	}
+	return false
+}
+
+evaluate_contains :: proc(attr: Attribute_Value, val: Attribute_Value) -> bool {
+	// For strings: substring check
+	#partial switch a in attr {
+	case String:
+		if v, ok := val.(String); ok {
+			return strings.contains(string(a), string(v))
+		}
+
+	case String_Set:
+		if v, ok := val.(String); ok {
+			for s in a {
+				if s == string(v) {
+					return true
+				}
+			}
+		}
+
+	case DDB_Number_Set:
+		if v, ok := val.(DDB_Number); ok {
+			for num in a {
+				if compare_ddb_numbers(num, v) == 0 {
+					return true
+				}
+			}
+		}
+
+	case List:
+		for item in a {
+			if compare_attribute_values(item, val) == 0 {
+				return true
+			}
+		}
+	}
+
+	return false
+}
+
+// Compare two AttributeValues. Returns <0, 0, or >0.
+// For mixed types, returns -2 (not comparable).
+compare_attribute_values :: proc(a: Attribute_Value, b: Attribute_Value) -> int {
+	a_str, a_ok := attr_value_to_string_for_compare(a)
+	b_str, b_ok := attr_value_to_string_for_compare(b)
+
+	if !a_ok || !b_ok {
+		// Try bool comparison
+		a_bool, a_is_bool := a.(Bool)
+		b_bool, b_is_bool := b.(Bool)
+		if a_is_bool && b_is_bool {
+			if bool(a_bool) == bool(b_bool) {
+				return 0
+			}
+			return -2
+		}
+		return -2
+	}
+
+	// For Numbers, do with DDB_Number comparison
+	_, a_is_num := a.(DDB_Number)
+	_, b_is_num := b.(DDB_Number)
+	if a_is_num && b_is_num {
+		a_num := a.(DDB_Number)
+		b_num := b.(DDB_Number)
+		return compare_ddb_numbers(a_num, b_num)
+	}
+
+	return strings.compare(a_str, b_str)
+}
+
+// ============================================================================
+// Request parsing helpers for FilterExpression
+// ============================================================================
+
+parse_filter_expression_string :: proc(request_body: []byte) -> (expr: string, ok: bool) {
+	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
+	if parse_err != nil {
+		return
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		return
+	}
+
+	fe_val, found := root["FilterExpression"]
+	if !found {
+		return
+	}
+
+	fe_str, str_ok := fe_val.(json.String)
+	if !str_ok {
+		return
+	}
+
+	expr = strings.clone(string(fe_str))
+	ok = true
+	return
+}
+
+// ============================================================================
+// Allocator Helper
+// ============================================================================
+
+make_filter_node :: proc() -> ^Filter_Node {
+	node := new(Filter_Node)
+	node.allocator = context.allocator
+	return node
+}

dynamodb/gsi.odin

@@ -0,0 +1,510 @@
+// Global Secondary Index (GSI) support
+//
+// DynamoDB GSI semantics:
+//   - GSI entries are maintained automatically on every write (put/delete/update)
+//   - Each GSI has its own key schema (partition key + optional sort key)
+//   - GSI keys are built from item attributes; if an item doesn't have the GSI
+//     key attribute(s), NO GSI entry is written (sparse index)
+//   - Projection controls which non-key attributes are stored in the GSI entry:
+//       ALL       → entire item is copied
+//       KEYS_ONLY → only table PK/SK + GSI PK/SK
+//       INCLUDE   → table keys + GSI keys + specified non-key attributes
+//   - Query on a GSI uses IndexName to route to the correct key prefix
+//
+// Storage layout:
+//   GSI key:   [0x03][table_name][index_name][gsi_pk_value][gsi_sk_value?]
+//   GSI value: TLV-encoded projected item (same binary format as regular items)
+//
+// Write path:
+//   put_item  → for each GSI, extract GSI key attrs from the NEW item, write GSI entry
+//   delete    → for each GSI, extract GSI key attrs from the OLD item, delete GSI entry
+//   update    → delete OLD GSI entries, write NEW GSI entries
+//
+// ATOMICITY: All GSI operations use WriteBatch to ensure that GSI entries are
+//            maintained atomically with the base item write/delete.
+//
+package dynamodb
+
+import "core:slice"
+import "core:strings"
+import "../rocksdb"
+
+// ============================================================================
+// GSI Key Extraction
+//
+// Extracts the GSI partition key (and optional sort key) raw bytes from an item.
+// Returns false if the item doesn't have the required GSI PK attribute (sparse).
+// ============================================================================
+
+GSI_Key_Values :: struct {
+	pk:  []byte,
+	sk:  Maybe([]byte),
+}
+
+// Extract GSI key values from an item based on the GSI's key schema.
+// Returns ok=false if ANY required key attribute is missing (sparse index).
+// DynamoDB sparse index semantics: item must have ALL key attributes defined in the GSI schema.
+gsi_extract_key_values :: proc(item: Item, gsi_key_schema: []Key_Schema_Element) -> (GSI_Key_Values, bool) {
+	result: GSI_Key_Values
+
+	for ks in gsi_key_schema {
+		attr, found := item[ks.attribute_name]
+		if !found {
+			// Any key attribute missing → sparse index, skip this item
+			return {}, false
+		}
+
+		raw, raw_ok := attr_value_to_bytes(attr)
+		if !raw_ok {
+			// Can't convert attribute to bytes → skip this item
+			return {}, false
+		}
+
+		switch ks.key_type {
+		case .HASH:
+			result.pk = raw
+		case .RANGE:
+			result.sk = raw
+		}
+	}
+
+	return result, true
+}
+
+// Convert a scalar attribute value to its raw byte representation (borrowed).
+attr_value_to_bytes :: proc(attr: Attribute_Value) -> ([]byte, bool) {
+	#partial switch v in attr {
+	case String:
+		return transmute([]byte)string(v), true
+	case DDB_Number:
+		return encode_ddb_number_for_sort(v), true
+	case Binary:
+		return transmute([]byte)string(v), true
+	}
+	return nil, false
+}
+
+// ============================================================================
+// GSI Projection
+//
+// Build a projected copy of an item for storage in a GSI entry.
+// ============================================================================
+
+// Build the projected item for a GSI entry.
+// The result is a new Item that the caller owns.
+gsi_project_item :: proc(
+	item: Item,
+	gsi: ^Global_Secondary_Index,
+	table_key_schema: []Key_Schema_Element,
+) -> Item {
+	switch gsi.projection.projection_type {
+	case .ALL:
+		return item_deep_copy(item)
+
+	case .KEYS_ONLY:
+		projected := make(Item)
+		// Include table key attributes
+		for ks in table_key_schema {
+			if val, found := item[ks.attribute_name]; found {
+				projected[strings.clone(ks.attribute_name)] = attr_value_deep_copy(val)
+			}
+		}
+		// Include GSI key attributes
+		for ks in gsi.key_schema {
+			if _, already := projected[ks.attribute_name]; already {
+				continue // Already included as table key
+			}
+			if val, found := item[ks.attribute_name]; found {
+				projected[strings.clone(ks.attribute_name)] = attr_value_deep_copy(val)
+			}
+		}
+		return projected
+
+	case .INCLUDE:
+		projected := make(Item)
+		// Include table key attributes
+		for ks in table_key_schema {
+			if val, found := item[ks.attribute_name]; found {
+				projected[strings.clone(ks.attribute_name)] = attr_value_deep_copy(val)
+			}
+		}
+		// Include GSI key attributes
+		for ks in gsi.key_schema {
+			if _, already := projected[ks.attribute_name]; already {
+				continue
+			}
+			if val, found := item[ks.attribute_name]; found {
+				projected[strings.clone(ks.attribute_name)] = attr_value_deep_copy(val)
+			}
+		}
+		// Include specified non-key attributes
+		if nka, has_nka := gsi.projection.non_key_attributes.?; has_nka {
+			for attr_name in nka {
+				if _, already := projected[attr_name]; already {
+					continue
+				}
+				if val, found := item[attr_name]; found {
+					projected[strings.clone(attr_name)] = attr_value_deep_copy(val)
+				}
+			}
+		}
+		return projected
+	}
+
+	// Fallback: all
+	return item_deep_copy(item)
+}
+
+// ============================================================================
+// GSI Write Maintenance - ATOMIC via WriteBatch
+//
+// These procedures add GSI operations to a WriteBatch instead of performing
+// direct database writes. This ensures atomicity with the base item operation.
+// ============================================================================
+
+// Add GSI write operations to a WriteBatch for an item across all GSIs.
+// Called during put_item or update_item to maintain NEW GSI entries.
+gsi_batch_write_entries :: proc(
+	batch: ^rocksdb.WriteBatch,
+	table_name: string,
+	item: Item,
+	metadata: ^Table_Metadata,
+) -> Storage_Error {
+	gsis, has_gsis := metadata.global_secondary_indexes.?
+	if !has_gsis || len(gsis) == 0 {
+		return .None
+	}
+
+	base_key, base_ok := key_from_item(item, metadata.key_schema)
+	if !base_ok {
+		return .Missing_Key_Attribute
+	}
+	defer key_destroy(&base_key)
+
+	base_vals, base_vals_ok := key_get_values(&base_key)
+	if !base_vals_ok {
+		return .Invalid_Key
+	}
+
+	for &gsi in gsis {
+		// Extract GSI key from item
+		gsi_kv, kv_ok := gsi_extract_key_values(item, gsi.key_schema)
+		if !kv_ok do continue // item doesn't have GSI PK, skip
+
+		// Build GSI storage key
+		gsi_storage_key := build_gsi_key(
+			table_name,
+			gsi.index_name,
+			gsi_kv.pk,
+			gsi_kv.sk,
+			base_vals.pk,
+			base_vals.sk,
+		)
+		defer delete(gsi_storage_key)
+
+		// Build projected item
+		projected := gsi_project_item(item, &gsi, metadata.key_schema)
+		defer item_destroy(&projected)
+
+		// Encode projected item
+		encoded, encode_ok := encode(projected)
+		if !encode_ok {
+			return .Serialization_Error
+		}
+		defer delete(encoded)
+
+		// Add to batch (not written yet)
+		rocksdb.batch_put(batch, gsi_storage_key, encoded)
+	}
+
+	return .None
+}
+
+// Add GSI delete operations to a WriteBatch for an item across all GSIs.
+// Called during delete_item or update_item to remove OLD GSI entries.
+// Needs the OLD item to know which GSI keys to remove.
+gsi_batch_delete_entries :: proc(
+	batch: ^rocksdb.WriteBatch,
+	table_name: string,
+	old_item: Item,
+	metadata: ^Table_Metadata,
+) -> Storage_Error {
+	gsis, has_gsis := metadata.global_secondary_indexes.?
+	if !has_gsis || len(gsis) == 0 {
+		return .None
+	}
+
+	base_key, base_ok := key_from_item(old_item, metadata.key_schema)
+	if !base_ok {
+		return .Missing_Key_Attribute
+	}
+	defer key_destroy(&base_key)
+
+	base_vals, base_vals_ok := key_get_values(&base_key)
+	if !base_vals_ok {
+		return .Invalid_Key
+	}
+
+	for &gsi in gsis {
+		// Extract GSI key from item
+		gsi_kv, kv_ok := gsi_extract_key_values(old_item, gsi.key_schema)
+		if !kv_ok do continue // old item doesn't have GSI PK, skip
+
+		// Build GSI storage key
+		gsi_storage_key := build_gsi_key(
+			table_name,
+			gsi.index_name,
+			gsi_kv.pk,
+			gsi_kv.sk,
+			base_vals.pk,
+			base_vals.sk,
+		)
+		defer delete(gsi_storage_key)
+
+		// Add to batch (not written yet)
+		rocksdb.batch_delete(batch, gsi_storage_key)
+	}
+
+	return .None
+}
+
+// ============================================================================
+// GSI Query
+//
+// Queries a GSI by partition key with optional sort key condition.
+// Mirrors the main table query() but uses GSI key prefix.
+// ============================================================================
+
+gsi_query :: proc(
+	engine: ^Storage_Engine,
+	table_name: string,
+	index_name: string,
+	partition_key_value: []byte,
+	exclusive_start_key: Maybe([]byte),
+	limit: int,
+	sk_condition: Maybe(Sort_Key_Condition) = nil,
+) -> (Query_Result, Storage_Error) {
+	// Build GSI partition prefix
+	prefix := build_gsi_partition_prefix(table_name, index_name, partition_key_value)
+	defer delete(prefix)
+
+	iter, iter_err := rocksdb.iter_create(&engine.db)
+	if iter_err != .None {
+		return {}, .RocksDB_Error
+	}
+	defer rocksdb.iter_destroy(&iter)
+
+	max_items := limit if limit > 0 else 1_000_000
+
+	// Seek to start position
+	if start_key, has_start := exclusive_start_key.?; has_start {
+		if has_prefix(start_key, prefix) {
+			rocksdb.iter_seek(&iter, start_key)
+			if rocksdb.iter_valid(&iter) {
+				rocksdb.iter_next(&iter)
+			}
+		} else {
+			rocksdb.iter_seek(&iter, prefix)
+		}
+	} else {
+		rocksdb.iter_seek(&iter, prefix)
+	}
+
+	items := make([dynamic]Item)
+	count := 0
+	last_key: Maybe([]byte) = nil
+	has_more := false
+
+	for rocksdb.iter_valid(&iter) {
+		key := rocksdb.iter_key(&iter)
+		if key == nil || !has_prefix(key, prefix) {
+			break
+		}
+
+		if count >= max_items {
+			has_more = true
+			break
+		}
+
+		value := rocksdb.iter_value(&iter)
+		if value == nil {
+			rocksdb.iter_next(&iter)
+			continue
+		}
+
+		item, decode_ok := decode(value)
+		if !decode_ok {
+			rocksdb.iter_next(&iter)
+			continue
+		}
+
+		// Sort key condition filtering
+		if skc, has_skc := sk_condition.?; has_skc {
+			if !evaluate_sort_key_condition(item, &skc) {
+				item_copy := item
+				item_destroy(&item_copy)
+				rocksdb.iter_next(&iter)
+				continue
+			}
+		}
+
+		append(&items, item)
+		count += 1
+
+		// Track key of last returned item
+		if prev_key, had_prev := last_key.?; had_prev {
+			delete(prev_key)
+		}
+		last_key = slice.clone(key)
+
+		rocksdb.iter_next(&iter)
+	}
+
+	// Only emit LastEvaluatedKey if there are more items
+	if !has_more {
+		if lk, had_lk := last_key.?; had_lk {
+			delete(lk)
+		}
+		last_key = nil
+	}
+
+	result_items := make([]Item, len(items))
+	copy(result_items, items[:])
+
+	return Query_Result{
+		items              = result_items,
+		last_evaluated_key = last_key,
+	}, .None
+}
+
+// ============================================================================
+// GSI Scan
+//
+// Scans all entries in a GSI (all partition keys under that index).
+// ============================================================================
+
+gsi_scan :: proc(
+	engine: ^Storage_Engine,
+	table_name: string,
+	index_name: string,
+	exclusive_start_key: Maybe([]byte),
+	limit: int,
+) -> (Scan_Result, Storage_Error) {
+	prefix := build_gsi_prefix(table_name, index_name)
+	defer delete(prefix)
+
+	iter, iter_err := rocksdb.iter_create(&engine.db)
+	if iter_err != .None {
+		return {}, .RocksDB_Error
+	}
+	defer rocksdb.iter_destroy(&iter)
+
+	max_items := limit if limit > 0 else 1_000_000
+
+	if start_key, has_start := exclusive_start_key.?; has_start {
+		if has_prefix(start_key, prefix) {
+			rocksdb.iter_seek(&iter, start_key)
+			if rocksdb.iter_valid(&iter) {
+				rocksdb.iter_next(&iter)
+			}
+		} else {
+			rocksdb.iter_seek(&iter, prefix)
+		}
+	} else {
+		rocksdb.iter_seek(&iter, prefix)
+	}
+
+	items := make([dynamic]Item)
+	count := 0
+	last_key: Maybe([]byte) = nil
+	has_more := false
+
+	for rocksdb.iter_valid(&iter) {
+		key := rocksdb.iter_key(&iter)
+		if key == nil || !has_prefix(key, prefix) {
+			break
+		}
+
+		if count >= max_items {
+			has_more = true
+			break
+		}
+
+		value := rocksdb.iter_value(&iter)
+		if value == nil {
+			rocksdb.iter_next(&iter)
+			continue
+		}
+
+		item, decode_ok := decode(value)
+		if !decode_ok {
+			rocksdb.iter_next(&iter)
+			continue
+		}
+
+		append(&items, item)
+		count += 1
+
+		if prev_key, had_prev := last_key.?; had_prev {
+			delete(prev_key)
+		}
+		last_key = slice.clone(key)
+
+		rocksdb.iter_next(&iter)
+	}
+
+	if !has_more {
+		if lk, had_lk := last_key.?; had_lk {
+			delete(lk)
+		}
+		last_key = nil
+	}
+
+	result_items := make([]Item, len(items))
+	copy(result_items, items[:])
+
+	return Scan_Result{
+		items              = result_items,
+		last_evaluated_key = last_key,
+	}, .None
+}
+
+// ============================================================================
+// GSI Metadata Lookup Helpers
+// ============================================================================
+
+// Find a GSI definition by index name in the table metadata.
+find_gsi :: proc(metadata: ^Table_Metadata, index_name: string) -> (^Global_Secondary_Index, bool) {
+	gsis, has_gsis := metadata.global_secondary_indexes.?
+	if !has_gsis {
+		return nil, false
+	}
+
+	for &gsi in gsis {
+		if gsi.index_name == index_name {
+			return &gsi, true
+		}
+	}
+
+	return nil, false
+}
+
+// Get the GSI's sort key attribute name (if any).
+gsi_get_sort_key_name :: proc(gsi: ^Global_Secondary_Index) -> Maybe(string) {
+	for ks in gsi.key_schema {
+		if ks.key_type == .RANGE {
+			return ks.attribute_name
+		}
+	}
+	return nil
+}
+
+// Get the GSI's partition key attribute name.
+gsi_get_partition_key_name :: proc(gsi: ^Global_Secondary_Index) -> Maybe(string) {
+	for ks in gsi.key_schema {
+		if ks.key_type == .HASH {
+			return ks.attribute_name
+		}
+	}
+	return nil
+}

dynamodb/gsi_metadata.odin

@@ -0,0 +1,187 @@
+// gsi_metadata.odin — GSI metadata parsing for serialize/deserialize_table_metadata
+//
+// Parses GSI definitions from the embedded JSON string stored in table metadata.
+// This file lives in the dynamodb/ package.
+package dynamodb
+
+import "core:encoding/json"
+import "core:mem"
+import "core:strings"
+
+// Parse GlobalSecondaryIndexes from a JSON string like:
+// [{"IndexName":"email-index","KeySchema":[{"AttributeName":"email","KeyType":"HASH"}],
+//   "Projection":{"ProjectionType":"ALL"}}]
+//
+// Allocates all strings with the given allocator (engine.allocator for long-lived data).
+parse_gsis_json :: proc(json_str: string, allocator: mem.Allocator) -> ([]Global_Secondary_Index, bool) {
+	data, parse_err := json.parse(transmute([]byte)json_str, allocator = context.temp_allocator)
+	if parse_err != nil {
+		return nil, false
+	}
+	defer json.destroy_value(data)
+
+	arr, ok := data.(json.Array)
+	if !ok {
+		return nil, false
+	}
+
+	if len(arr) == 0 {
+		return nil, true // Empty is valid
+	}
+
+	result := make([]Global_Secondary_Index, len(arr), allocator)
+
+	for elem, i in arr {
+		obj, obj_ok := elem.(json.Object)
+		if !obj_ok {
+			cleanup_gsis(result[:i], allocator)
+			delete(result, allocator)
+			return nil, false
+		}
+
+		gsi, gsi_ok := parse_single_gsi_json(obj, allocator)
+		if !gsi_ok {
+			cleanup_gsis(result[:i], allocator)
+			delete(result, allocator)
+			return nil, false
+		}
+
+		result[i] = gsi
+	}
+
+	return result, true
+}
+
+// Parse a single GSI object from JSON
+@(private = "file")
+parse_single_gsi_json :: proc(obj: json.Object, allocator: mem.Allocator) -> (Global_Secondary_Index, bool) {
+	gsi: Global_Secondary_Index
+
+	// IndexName
+	idx_val, idx_found := obj["IndexName"]
+	if !idx_found {
+		return {}, false
+	}
+	idx_str, idx_ok := idx_val.(json.String)
+	if !idx_ok {
+		return {}, false
+	}
+	gsi.index_name = strings.clone(string(idx_str), allocator)
+
+	// KeySchema
+	ks_val, ks_found := obj["KeySchema"]
+	if !ks_found {
+		delete(gsi.index_name, allocator)
+		return {}, false
+	}
+	ks_arr, ks_ok := ks_val.(json.Array)
+	if !ks_ok || len(ks_arr) == 0 || len(ks_arr) > 2 {
+		delete(gsi.index_name, allocator)
+		return {}, false
+	}
+
+	key_schema := make([]Key_Schema_Element, len(ks_arr), allocator)
+	for ks_elem, j in ks_arr {
+		ks_obj, kobj_ok := ks_elem.(json.Object)
+		if !kobj_ok {
+			for k in 0..<j {
+				delete(key_schema[k].attribute_name, allocator)
+			}
+			delete(key_schema, allocator)
+			delete(gsi.index_name, allocator)
+			return {}, false
+		}
+
+		an_val, an_found := ks_obj["AttributeName"]
+		if !an_found {
+			for k in 0..<j { delete(key_schema[k].attribute_name, allocator) }
+			delete(key_schema, allocator)
+			delete(gsi.index_name, allocator)
+			return {}, false
+		}
+		an_str, an_ok := an_val.(json.String)
+		if !an_ok {
+			for k in 0..<j { delete(key_schema[k].attribute_name, allocator) }
+			delete(key_schema, allocator)
+			delete(gsi.index_name, allocator)
+			return {}, false
+		}
+
+		kt_val, kt_found := ks_obj["KeyType"]
+		if !kt_found {
+			for k in 0..<j { delete(key_schema[k].attribute_name, allocator) }
+			delete(key_schema, allocator)
+			delete(gsi.index_name, allocator)
+			return {}, false
+		}
+		kt_str, kt_ok := kt_val.(json.String)
+		if !kt_ok {
+			for k in 0..<j { delete(key_schema[k].attribute_name, allocator) }
+			delete(key_schema, allocator)
+			delete(gsi.index_name, allocator)
+			return {}, false
+		}
+
+		kt, kt_parse_ok := key_type_from_string(string(kt_str))
+		if !kt_parse_ok {
+			for k in 0..<j { delete(key_schema[k].attribute_name, allocator) }
+			delete(key_schema, allocator)
+			delete(gsi.index_name, allocator)
+			return {}, false
+		}
+
+		key_schema[j] = Key_Schema_Element{
+			attribute_name = strings.clone(string(an_str), allocator),
+			key_type = kt,
+		}
+	}
+	gsi.key_schema = key_schema
+
+	// Projection
+	gsi.projection.projection_type = .ALL // default
+	if proj_val, proj_found := obj["Projection"]; proj_found {
+		if proj_obj, proj_ok := proj_val.(json.Object); proj_ok {
+			if pt_val, pt_found := proj_obj["ProjectionType"]; pt_found {
+				if pt_str, pt_ok := pt_val.(json.String); pt_ok {
+					switch string(pt_str) {
+					case "ALL":       gsi.projection.projection_type = .ALL
+					case "KEYS_ONLY": gsi.projection.projection_type = .KEYS_ONLY
+					case "INCLUDE":   gsi.projection.projection_type = .INCLUDE
+					}
+				}
+			}
+
+			// NonKeyAttributes
+			if nka_val, nka_found := proj_obj["NonKeyAttributes"]; nka_found {
+				if nka_arr, nka_ok := nka_val.(json.Array); nka_ok && len(nka_arr) > 0 {
+					nka := make([]string, len(nka_arr), allocator)
+					for attr_val, k in nka_arr {
+						if attr_str, attr_ok := attr_val.(json.String); attr_ok {
+							nka[k] = strings.clone(string(attr_str), allocator)
+						}
+					}
+					gsi.projection.non_key_attributes = nka
+				}
+			}
+		}
+	}
+
+	return gsi, true
+}
+
+// Clean up partially-constructed GSI array
+cleanup_gsis :: proc(gsis: []Global_Secondary_Index, allocator: mem.Allocator) {
+	for gsi in gsis {
+		delete(gsi.index_name, allocator)
+		for ks in gsi.key_schema {
+			delete(ks.attribute_name, allocator)
+		}
+		delete(gsi.key_schema, allocator)
+		if nka, has_nka := gsi.projection.non_key_attributes.?; has_nka {
+			for attr in nka {
+				delete(attr, allocator)
+			}
+			delete(nka, allocator)
+		}
+	}
+}

dynamodb/item_codec.odin

@@ -76,10 +76,12 @@ encode_attribute_value :: proc(buf: ^bytes.Buffer, attr: Attribute_Value) -> boo
 		encode_varint(buf, len(v))
 		bytes.buffer_write_string(buf, string(v))
 
-	case Number:
+	case DDB_Number:
 		bytes.buffer_write_byte(buf, u8(Type_Tag.Number))
-		encode_varint(buf, len(v))
+		// Store as string in item encoding
-		bytes.buffer_write_string(buf, string(v))
+		num_str := format_ddb_number(v)
+		encode_varint(buf, len(num_str))
+		bytes.buffer_write_string(buf, num_str)
 
 	case Binary:
 		bytes.buffer_write_byte(buf, u8(Type_Tag.Binary))
@@ -94,6 +96,16 @@ encode_attribute_value :: proc(buf: ^bytes.Buffer, attr: Attribute_Value) -> boo
 		bytes.buffer_write_byte(buf, u8(Type_Tag.Null))
 		// NULL has no value bytes
 
+	case DDB_Number_Set:
+		bytes.buffer_write_byte(buf, u8(Type_Tag.Number_Set))  // Use Number_Set tag, not DDB_Number_Set
+		encode_varint(buf, len(v))
+		for num in v {
+			// Format the DDB_Number to a string
+			num_str := format_ddb_number(num)
+			encode_varint(buf, len(num_str))
+			bytes.buffer_write_string(buf, num_str)
+		}
+
 	case String_Set:
 		bytes.buffer_write_byte(buf, u8(Type_Tag.String_Set))
 		encode_varint(buf, len(v))
@@ -102,14 +114,6 @@ encode_attribute_value :: proc(buf: ^bytes.Buffer, attr: Attribute_Value) -> boo
 			bytes.buffer_write_string(buf, s)
 		}
 
-	case Number_Set:
-		bytes.buffer_write_byte(buf, u8(Type_Tag.Number_Set))
-		encode_varint(buf, len(v))
-		for n in v {
-			encode_varint(buf, len(n))
-			bytes.buffer_write_string(buf, n)
-		}
-
 	case Binary_Set:
 		bytes.buffer_write_byte(buf, u8(Type_Tag.Binary_Set))
 		encode_varint(buf, len(v))
@@ -289,9 +293,15 @@ decode_attribute_value :: proc(decoder: ^Binary_Decoder) -> (Attribute_Value, bo
 			return nil, false
 		}
 
-		str := string(data)
+		num_str := string(data)
-		owned := transmute(string)slice.clone(transmute([]byte)str)
+
-		return Number(owned), true
+		// Parse into DDB_Number
+		ddb_num, num_ok := parse_ddb_number(num_str)
+		if !num_ok {
+			return nil, false
+		}
+
+		return ddb_num, true
 
 	case .Binary:
 		length, len_ok := decoder_read_varint(decoder)
@@ -359,32 +369,35 @@ decode_attribute_value :: proc(decoder: ^Binary_Decoder) -> (Attribute_Value, bo
 			return nil, false
 		}
 
-		numbers := make([]string, count)
+		numbers := make([]DDB_Number, count)  // Changed to DDB_Number
 
 		for i in 0..<count {
 			length, len_ok := decoder_read_varint(decoder)
 			if !len_ok {
-				for j in 0..<i {
+				// No cleanup needed for DDB_Number (no heap allocations)
-					delete(numbers[j])
-				}
 				delete(numbers)
 				return nil, false
 			}
 
 			data, data_ok := decoder_read_bytes(decoder, length)
 			if !data_ok {
-				for j in 0..<i {
-					delete(numbers[j])
-				}
 				delete(numbers)
 				return nil, false
 			}
 
-			str := string(data)
+			num_str := string(data)
-			numbers[i] = transmute(string)slice.clone(transmute([]byte)str)
+
+			// Parse into DDB_Number
+			ddb_num, num_ok := parse_ddb_number(num_str)
+			if !num_ok {
+				delete(numbers)
+				return nil, false
+			}
+
+			numbers[i] = ddb_num
 		}
 
-		return Number_Set(numbers), true
+		return DDB_Number_Set(numbers), true
 
 	case .Binary_Set:
 		count, count_ok := decoder_read_varint(decoder)

dynamodb/json.odin

@@ -85,7 +85,16 @@ parse_attribute_value :: proc(value: json.Value) -> (Attribute_Value, bool) {
 			if !str_ok {
 				return nil, false
 			}
-			return Number(strings.clone(string(str))), true
+
+			// Parse into DDB_Number
+			ddb_num, num_ok := parse_ddb_number(string(str))
+			if !num_ok {
+				return nil, false
+			}
+
+			// Clone the string fields since they're slices of the input
+			owned_num := clone_ddb_number(ddb_num)
+			return owned_num, true
 		}
 
 		// Binary (base64 string)
@@ -147,22 +156,38 @@ parse_attribute_value :: proc(value: json.Value) -> (Attribute_Value, bool) {
 				return nil, false
 			}
 
-			numbers_arr := make([]string, len(arr))
+			numbers_arr := make([]DDB_Number, len(arr))
 
 			for item, i in arr {
 				str, str_ok := item.(json.String)
 				if !str_ok {
 					// Cleanup on error
 					for j in 0..<i {
-						delete(numbers_arr[j])
+						// Clean up DDB_Numbers
+						delete(numbers_arr[j].integer_part)
+						delete(numbers_arr[j].fractional_part)
 					}
 					delete(numbers_arr)
 					return nil, false
 				}
-				numbers_arr[i] = strings.clone(string(str))
+
+				// Parse into DDB_Number
+				ddb_num, num_ok := parse_ddb_number(string(str))
+				if !num_ok {
+					// Cleanup on error
+					for j in 0..<i {
+						delete(numbers_arr[j].integer_part)
+						delete(numbers_arr[j].fractional_part)
+					}
+					delete(numbers_arr)
+					return nil, false
+				}
+
+				// Clone and store
+				numbers_arr[i] = clone_ddb_number(ddb_num)
 			}
 
-			return Number_Set(numbers_arr), true
+			return DDB_Number_Set(numbers_arr), true
 		}
 
 		// Binary Set
@@ -297,16 +322,25 @@ serialize_item_to_builder :: proc(b: ^strings.Builder, item: Item) {
 serialize_attribute_value :: proc(b: ^strings.Builder, attr: Attribute_Value) {
 	switch v in attr {
 	case String:
-		fmt.sbprintf(b, `{"S":"%s"}`, string(v))
+		strings.write_string(b, `{"S":"`)
+		strings.write_string(b, string(v))
+		strings.write_string(b, `"}`)
 
-	case Number:
+	case DDB_Number:
-		fmt.sbprintf(b, `{"N":"%s"}`, string(v))
+		num_str := format_ddb_number(v)
+		strings.write_string(b, `{"N":"`)
+		strings.write_string(b, num_str)
+		strings.write_string(b, `"}`)
 
 	case Binary:
-		fmt.sbprintf(b, `{"B":"%s"}`, string(v))
+		strings.write_string(b, `{"B":"`)
+		strings.write_string(b, string(v))
+		strings.write_string(b, `"}`)
 
 	case Bool:
-		fmt.sbprintf(b, `{"BOOL":%v}`, bool(v))
+		strings.write_string(b, `{"BOOL":`)
+		if bool(v) { strings.write_string(b, "true") } else { strings.write_string(b, "false") }
+		strings.write_string(b, "}")
 
 	case Null:
 		strings.write_string(b, `{"NULL":true}`)
@@ -321,13 +355,14 @@ serialize_attribute_value :: proc(b: ^strings.Builder, attr: Attribute_Value) {
 		}
 		strings.write_string(b, "]}")
 
-	case Number_Set:
+	case DDB_Number_Set:
 		strings.write_string(b, `{"NS":[`)
-		for n, i in v {
+		for num, i in v {
 			if i > 0 {
 				strings.write_string(b, ",")
 			}
-			fmt.sbprintf(b, `"%s"`, n)
+			num_str := format_ddb_number(num)
+			fmt.sbprintf(b, `"%s"`, num_str)
 		}
 		strings.write_string(b, "]}")
 
@@ -404,7 +439,7 @@ parse_table_name :: proc(request_body: []byte) -> (string, bool) {
 		return "", false
 	}
 
-	return string(table_name_str), true
+	return strings.clone(string(table_name_str)), true
 }
 
 // Parse Item field from request body
@@ -494,45 +529,49 @@ parse_limit :: proc(request_body: []byte) -> int {
 // Returns nil (not an error) when the field is absent.
 // ============================================================================
 
+// Returns (key, ok, body_parse_err).
+//   ok=true,  body_parse_err=false → key present and valid, or key absent (no pagination)
+//   ok=false, body_parse_err=true  → request body is not valid JSON or not an object
+//   ok=false, body_parse_err=false → ExclusiveStartKey present but malformed/invalid
 parse_exclusive_start_key :: proc(
 	request_body: []byte,
 	table_name: string,
 	key_schema: []Key_Schema_Element,
-) -> (result: Maybe([]byte), ok: bool) {
+) -> (result: Maybe([]byte), ok: bool, body_err: bool) {
 	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
 	if parse_err != nil {
-		return nil, true // no ESK is fine
+		return nil, false, true // body is not valid JSON — real error
 	}
 	defer json.destroy_value(data)
 
 	root, root_ok := data.(json.Object)
 	if !root_ok {
-		return nil, true
+		return nil, false, true // root must be an object — real error
 	}
 
 	esk_val, found := root["ExclusiveStartKey"]
 	if !found {
-		return nil, true // absent → no pagination, that's ok
+		return nil, true, false // absent → no pagination, that's ok
 	}
 
 	// Parse ExclusiveStartKey as a DynamoDB Item
 	key_item, item_ok := parse_item_from_value(esk_val)
 	if !item_ok {
-		return nil, false // present but malformed → real error
+		return nil, false, false // present but malformed → validation error
 	}
 	defer item_destroy(&key_item)
 
 	// Validate and extract key struct using schema
 	key_struct, key_ok := key_from_item(key_item, key_schema)
 	if !key_ok {
-		return nil, false // missing required key attributes
+		return nil, false, false // missing required key attributes
 	}
 	defer key_destroy(&key_struct)
 
 	// Get raw byte values
 	key_values, kv_ok := key_get_values(&key_struct)
 	if !kv_ok {
-		return nil, false
+		return nil, false, false
 	}
 
 	// Build binary storage key
@@ -542,6 +581,53 @@ parse_exclusive_start_key :: proc(
 	return
 }
 
+// parse_exclusive_start_key_gsi ... Just a helper for GSI keys
+// Returns (key, ok, body_parse_err) — same contract as parse_exclusive_start_key.
+parse_exclusive_start_key_gsi :: proc(
+	request_body: []byte,
+	table_name: string,
+	metadata: ^Table_Metadata,
+	gsi: ^Global_Secondary_Index,
+) -> (Maybe([]byte), bool, bool) {
+	root, parse_err := json.parse(request_body)
+	if parse_err != nil do return nil, false, true // body not valid JSON
+	defer json.destroy_value(root)
+
+	obj, obj_ok := root.(json.Object)
+	if !obj_ok do return nil, false, true // root must be an object
+
+	esk_val, has := obj["ExclusiveStartKey"]
+	if !has do return nil, true, false // absent → no pagination
+
+	key_item, key_ok := parse_item_from_value(esk_val)
+	if !key_ok do return nil, false, false
+	defer item_destroy(&key_item)
+
+	idx_key, idx_ok := key_from_item(key_item, gsi.key_schema)
+	if !idx_ok do return nil, false, false
+	defer key_destroy(&idx_key)
+
+	idx_vals, idx_vals_ok := key_get_values(&idx_key)
+	if !idx_vals_ok do return nil, false, false
+
+	base_key, base_ok := key_from_item(key_item, metadata.key_schema)
+	if !base_ok do return nil, false, false
+	defer key_destroy(&base_key)
+
+	base_vals, base_vals_ok := key_get_values(&base_key)
+	if !base_vals_ok do return nil, false, false
+
+	k := build_gsi_key(
+		table_name,
+		gsi.index_name,
+		idx_vals.pk,
+		idx_vals.sk,
+		base_vals.pk,
+		base_vals.sk,
+	)
+	return k, true, false
+}
+
 // ============================================================================
 // LastEvaluatedKey Generation (Pagination Output)
 //
@@ -613,3 +699,122 @@ serialize_last_evaluated_key :: proc(
 
 	return serialize_item(item), true
 }
+
+Decoded_GSI_Key_Full :: struct {
+	gsi_pk:  []byte,
+	gsi_sk:  Maybe([]byte),
+	base_pk: []byte,
+	base_sk: Maybe([]byte),
+}
+
+// Decode binary GSI key:
+//
+//   [gsi][table_name][index_name][gsi_pk][gsi_sk?][base_pk][base_sk?]
+//
+// Presence of gsi_sk/base_sk depends on whether the index/table has a RANGE key.
+decode_gsi_key_full_borrowed :: proc(
+	binary_key: []byte,
+	gsi_has_sort_key: bool,
+	table_has_sort_key: bool,
+) -> (result: Decoded_GSI_Key_Full, ok: bool) {
+	decoder := Key_Decoder{data = binary_key, pos = 0}
+
+	et := decoder_read_entity_type(&decoder) or_return
+	if et != .GSI {
+		return {}, false
+	}
+
+	// Skip table name + index name
+	_ = decoder_read_segment_borrowed(&decoder) or_return
+	_ = decoder_read_segment_borrowed(&decoder) or_return
+
+	// Read GSI PK
+	result.gsi_pk = decoder_read_segment_borrowed(&decoder) or_return
+
+	// Read GSI SK if index has one
+	if gsi_has_sort_key {
+		sk := decoder_read_segment_borrowed(&decoder) or_return
+		result.gsi_sk = sk
+	}
+
+	// Read base PK
+	result.base_pk = decoder_read_segment_borrowed(&decoder) or_return
+
+	// Read base SK if table has one
+	if table_has_sort_key {
+		sk := decoder_read_segment_borrowed(&decoder) or_return
+		result.base_sk = sk
+	}
+
+	return result, true
+}
+
+
+// Serialize a binary *GSI* key into a DynamoDB LastEvaluatedKey JSON object.
+// The output must include the *index* key attrs + the *base table* primary key attrs,
+// so boto can round-trip ExclusiveStartKey correctly.
+serialize_last_evaluated_key_gsi :: proc(
+	binary_key: []byte,
+	metadata: ^Table_Metadata,
+	gsi: ^Global_Secondary_Index,
+) -> (result: string, ok: bool) {
+
+	// Determine whether index/table have range keys
+	_, gsi_has_sk := gsi_get_sort_key_name(gsi).?
+	_, tbl_has_sk := table_metadata_get_sort_key_name(metadata).?
+
+	decoded, dec_ok := decode_gsi_key_full_borrowed(binary_key, gsi_has_sk, tbl_has_sk)
+	if !dec_ok {
+		return "", false
+	}
+
+	// Resolve key attribute names + types
+	idx_pk_name := gsi_get_partition_key_name(gsi).? or_return
+	idx_pk_type := table_metadata_get_attribute_type(metadata, idx_pk_name).? or_return
+
+	idx_sk_name: Maybe(string) = gsi_get_sort_key_name(gsi)
+	idx_sk_type: Maybe(Scalar_Attribute_Type) = nil
+	if n, has := idx_sk_name.?; has {
+		idx_sk_type = table_metadata_get_attribute_type(metadata, n)
+	}
+
+	base_pk_name := table_metadata_get_partition_key_name(metadata).? or_return
+	base_pk_type := table_metadata_get_attribute_type(metadata, base_pk_name).? or_return
+
+	base_sk_name: Maybe(string) = table_metadata_get_sort_key_name(metadata)
+	base_sk_type: Maybe(Scalar_Attribute_Type) = nil
+	if n, has := base_sk_name.?; has {
+		base_sk_type = table_metadata_get_attribute_type(metadata, n)
+	}
+
+	// Build LEK item
+	lek := make(Item)
+	defer item_destroy(&lek)
+
+	add_attr_once :: proc(item: ^Item, name: string, raw: []byte, t: Scalar_Attribute_Type) {
+		if _, exists := item^[name]; exists {
+			return
+		}
+		item^[strings.clone(name)] = build_attribute_value_with_type(raw, t)
+	}
+
+	// Index keys
+	add_attr_once(&lek, idx_pk_name, decoded.gsi_pk, idx_pk_type)
+
+	if sk_raw, has := decoded.gsi_sk.?; has {
+		skn := idx_sk_name.? or_return
+		skt := idx_sk_type.? or_return
+		add_attr_once(&lek, skn, sk_raw, skt)
+	}
+
+	// Base table keys
+	add_attr_once(&lek, base_pk_name, decoded.base_pk, base_pk_type)
+
+	if sk_raw, has := decoded.base_sk.?; has {
+		skn := base_sk_name.? or_return
+		skt := base_sk_type.? or_return
+		add_attr_once(&lek, skn, sk_raw, skt)
+	}
+
+	return serialize_item(lek), true
+}

dynamodb/key_codec.odin

@@ -130,32 +130,43 @@ build_partition_prefix :: proc(table_name: string, pk_value: []byte) -> []byte {
 	return bytes.buffer_to_bytes(&buf)
 }
 
-// Build GSI key: [gsi][table_name][index_name][gsi_pk][gsi_sk?]
+// Build GSI key: [gsi][table_name][index_name][gsi_pk][gsi_sk?][base_pk][base_sk?]
-build_gsi_key :: proc(table_name: string, index_name: string, gsi_pk: []byte, gsi_sk: Maybe([]byte)) -> []byte {
+build_gsi_key :: proc(
+	table_name: string,
+	index_name: string,
+	gsi_pk: []byte,
+	gsi_sk: Maybe([]byte),
+	base_pk: []byte,
+	base_sk: Maybe([]byte),
+) -> []byte {
 	buf: bytes.Buffer
 	bytes.buffer_init_allocator(&buf, 0, 512, context.allocator)
 
-	// Write entity type
 	bytes.buffer_write_byte(&buf, u8(Entity_Type.GSI))
 
-	// Write table name
 	encode_varint(&buf, len(table_name))
 	bytes.buffer_write_string(&buf, table_name)
 
-	// Write index name
 	encode_varint(&buf, len(index_name))
 	bytes.buffer_write_string(&buf, index_name)
 
-	// Write GSI partition key
 	encode_varint(&buf, len(gsi_pk))
 	bytes.buffer_write(&buf, gsi_pk)
 
-	// Write GSI sort key if present
 	if sk, ok := gsi_sk.?; ok {
 		encode_varint(&buf, len(sk))
 		bytes.buffer_write(&buf, sk)
 	}
 
+	// tie-breaker: base table primary key
+	encode_varint(&buf, len(base_pk))
+	bytes.buffer_write(&buf, base_pk)
+
+	if sk, ok := base_sk.?; ok {
+		encode_varint(&buf, len(sk))
+		bytes.buffer_write(&buf, sk)
+	}
+
 	return bytes.buffer_to_bytes(&buf)
 }
 

dynamodb/key_codec_gsi.odin

@@ -0,0 +1,94 @@
+// key_codec_gsi.odin — Additional key codec functions for GSI support
+//
+// These procedures complement key_codec.odin with prefix builders needed
+// for GSI scanning and querying. They follow the same encoding conventions:
+//   [entity_type][varint_len][segment_bytes]...
+//
+// Add the contents of this file to key_codec.odin (or keep as a separate file
+// in the dynamodb/ package).
+package dynamodb
+
+import "core:bytes"
+
+// Build GSI index prefix for scanning all entries in a GSI:
+//   [gsi][table_name][index_name]
+build_gsi_prefix :: proc(table_name: string, index_name: string) -> []byte {
+	buf: bytes.Buffer
+	bytes.buffer_init_allocator(&buf, 0, 256, context.allocator)
+
+	bytes.buffer_write_byte(&buf, u8(Entity_Type.GSI))
+
+	encode_varint(&buf, len(table_name))
+	bytes.buffer_write_string(&buf, table_name)
+
+	encode_varint(&buf, len(index_name))
+	bytes.buffer_write_string(&buf, index_name)
+
+	return bytes.buffer_to_bytes(&buf)
+}
+
+// Build GSI partition prefix for querying within a single partition:
+//   [gsi][table_name][index_name][pk_value]
+build_gsi_partition_prefix :: proc(table_name: string, index_name: string, pk_value: []byte) -> []byte {
+	buf: bytes.Buffer
+	bytes.buffer_init_allocator(&buf, 0, 512, context.allocator)
+
+	bytes.buffer_write_byte(&buf, u8(Entity_Type.GSI))
+
+	encode_varint(&buf, len(table_name))
+	bytes.buffer_write_string(&buf, table_name)
+
+	encode_varint(&buf, len(index_name))
+	bytes.buffer_write_string(&buf, index_name)
+
+	encode_varint(&buf, len(pk_value))
+	bytes.buffer_write(&buf, pk_value)
+
+	return bytes.buffer_to_bytes(&buf)
+}
+
+// Decode a GSI key back into components
+Decoded_GSI_Key :: struct {
+	table_name: string,
+	index_name: string,
+	pk_value:   []byte,
+	sk_value:   Maybe([]byte),
+}
+
+decode_gsi_key :: proc(key: []byte) -> (result: Decoded_GSI_Key, ok: bool) {
+	decoder := Key_Decoder{data = key, pos = 0}
+
+	entity_type := decoder_read_entity_type(&decoder) or_return
+	if entity_type != .GSI {
+		return {}, false
+	}
+
+	table_name_bytes := decoder_read_segment(&decoder) or_return
+	result.table_name = string(table_name_bytes)
+
+	index_name_bytes := decoder_read_segment(&decoder) or_return
+	result.index_name = string(index_name_bytes)
+
+	result.pk_value = decoder_read_segment(&decoder) or_return
+
+	if decoder_has_more(&decoder) {
+		sk := decoder_read_segment(&decoder) or_return
+		result.sk_value = sk
+	}
+
+	return result, true
+}
+
+// Build GSI prefix for deleting all GSI entries for a table (used by delete_table)
+//   [gsi][table_name]
+build_gsi_table_prefix :: proc(table_name: string) -> []byte {
+	buf: bytes.Buffer
+	bytes.buffer_init_allocator(&buf, 0, 256, context.allocator)
+
+	bytes.buffer_write_byte(&buf, u8(Entity_Type.GSI))
+
+	encode_varint(&buf, len(table_name))
+	bytes.buffer_write_string(&buf, table_name)
+
+	return bytes.buffer_to_bytes(&buf)
+}

dynamodb/number.odin

@@ -0,0 +1,796 @@
+package dynamodb
+
+import "core:fmt"
+import "core:strconv"
+import "core:strings"
+import "core:bytes"
+
+// ============================================================================
+// DynamoDB Number Type
+//
+// DynamoDB numbers are arbitrary-precision decimals with up to 38 digits of
+// precision. They can be positive, negative, or zero.
+//
+// We store numbers internally as:
+// - sign: bool (true = positive/zero, false = negative)
+// - integer_part: string (digits only, no sign)
+// - fractional_part: string (digits only, if any)
+// - exponent: i32 (for scientific notation, if needed)
+//
+// This preserves the original precision and allows proper ordering.
+// ============================================================================
+
+DDB_Number :: struct {
+	sign:            bool,   // true = positive/zero, false = negative
+	integer_part:    string, // digits only (e.g., "123")
+	fractional_part: string, // digits only (e.g., "456" for .456)
+	exponent:        i32,    // scientific notation exponent (usually 0)
+}
+
+// Parse a number string into DDB_Number
+// Supports formats: "123", "-123", "123.456", "1.23e10", "-1.23e-5"
+parse_ddb_number :: proc(s: string) -> (DDB_Number, bool) {
+	if len(s) == 0 {
+		return {}, false
+	}
+
+	num: DDB_Number
+	str := s
+
+	// Parse sign
+	if str[0] == '-' {
+		num.sign = false
+		str = str[1:]
+	} else if str[0] == '+' {
+		num.sign = true
+		str = str[1:]
+	} else {
+		num.sign = true
+	}
+
+	if len(str) == 0 {
+		return {}, false
+	}
+
+	// Find exponent if present (e or E)
+	exp_pos := -1
+	for i in 0..<len(str) {
+		if str[i] == 'e' || str[i] == 'E' {
+			exp_pos = i
+			break
+		}
+	}
+
+	// Parse mantissa
+	mantissa := str
+	if exp_pos >= 0 {
+		mantissa = str[:exp_pos]
+		exp_str := str[exp_pos+1:]
+		exp_val, exp_ok := strconv.parse_i64(exp_str)
+		if !exp_ok {
+			return {}, false
+		}
+		num.exponent = i32(exp_val)
+	}
+
+	// Find decimal point
+	dot_pos := -1
+	for i in 0..<len(mantissa) {
+		if mantissa[i] == '.' {
+			dot_pos = i
+			break
+		}
+	}
+
+	// Parse integer and fractional parts
+	if dot_pos >= 0 {
+		num.integer_part = mantissa[:dot_pos]
+		num.fractional_part = mantissa[dot_pos+1:]
+
+		// Validate fractional part
+		for c in num.fractional_part {
+			if c < '0' || c > '9' {
+				return {}, false
+			}
+		}
+	} else {
+		num.integer_part = mantissa
+	}
+
+	// Validate integer part (at least one digit, all digits)
+	if len(num.integer_part) == 0 {
+		num.integer_part = "0"
+	}
+	for c in num.integer_part {
+		if c < '0' || c > '9' {
+			return {}, false
+		}
+	}
+
+	// Normalize: remove leading zeros from integer part (except if it's just "0")
+	num = normalize_ddb_number(num)
+
+	// Check precision (DynamoDB supports up to 38 digits)
+	total_digits := len(num.integer_part) + len(num.fractional_part)
+	if total_digits > 38 {
+		return {}, false
+	}
+
+	// Special case: if the number is zero
+	if is_ddb_number_zero(num) {
+		num.sign = true
+		num.exponent = 0
+	}
+
+	return num, true
+}
+
+// Normalize a DDB_Number (remove leading zeros, trailing fractional zeros)
+normalize_ddb_number :: proc(num: DDB_Number) -> DDB_Number {
+	result := num
+
+	// Remove leading zeros from integer part
+	int_part := num.integer_part
+	for len(int_part) > 1 && int_part[0] == '0' {
+		int_part = int_part[1:]
+	}
+	result.integer_part = int_part
+
+	// Remove trailing zeros from fractional part
+	frac_part := num.fractional_part
+	for len(frac_part) > 0 && frac_part[len(frac_part)-1] == '0' {
+		frac_part = frac_part[:len(frac_part)-1]
+	}
+	result.fractional_part = frac_part
+
+	return result
+}
+
+// Check if a DDB_Number represents zero
+is_ddb_number_zero :: proc(num: DDB_Number) -> bool {
+	// Check if integer part is all zeros
+	for c in num.integer_part {
+		if c != '0' {
+			return false
+		}
+	}
+	// Check if fractional part is all zeros
+	for c in num.fractional_part {
+		if c != '0' {
+			return false
+		}
+	}
+	return true
+}
+
+// Convert DDB_Number to string representation
+ddb_number_to_string :: proc(num: DDB_Number) -> string {
+	builder := strings.builder_make()
+
+	if !num.sign {
+		strings.write_string(&builder, "-")
+	}
+
+	strings.write_string(&builder, num.integer_part)
+
+	if len(num.fractional_part) > 0 {
+		strings.write_string(&builder, ".")
+		strings.write_string(&builder, num.fractional_part)
+	}
+
+	if num.exponent != 0 {
+		fmt.sbprintf(&builder, "e%d", num.exponent)
+	}
+
+	return strings.to_string(builder)
+}
+
+// Compare two DDB_Numbers
+// Returns: -1 if a < b, 0 if a == b, 1 if a > b
+compare_ddb_numbers :: proc(a: DDB_Number, b: DDB_Number) -> int {
+	// Handle zero cases
+	a_zero := is_ddb_number_zero(a)
+	b_zero := is_ddb_number_zero(b)
+
+	if a_zero && b_zero {
+		return 0
+	}
+	if a_zero {
+		return b.sign ? -1 : 1  // 0 < positive, 0 > negative
+	}
+	if b_zero {
+		return a.sign ? 1 : -1  // positive > 0, negative < 0
+	}
+
+	// Different signs
+	if a.sign != b.sign {
+		return a.sign ? 1 : -1  // positive > negative
+	}
+
+	// Same sign - compare magnitudes
+	mag_cmp := compare_ddb_number_magnitudes(a, b)
+
+	// If negative, reverse the comparison
+	if !a.sign {
+		return -mag_cmp
+	}
+	return mag_cmp
+}
+
+// Compare magnitudes (absolute values) of two DDB_Numbers
+compare_ddb_number_magnitudes :: proc(a: DDB_Number, b: DDB_Number) -> int {
+	// Adjust for exponents first
+	a_adj := adjust_for_exponent(a)
+	b_adj := adjust_for_exponent(b)
+
+	// Compare integer parts length
+	if len(a_adj.integer_part) != len(b_adj.integer_part) {
+		return len(a_adj.integer_part) > len(b_adj.integer_part) ? 1 : -1
+	}
+
+	// Compare integer parts digit by digit
+	for i in 0..<len(a_adj.integer_part) {
+		if a_adj.integer_part[i] != b_adj.integer_part[i] {
+			return a_adj.integer_part[i] > b_adj.integer_part[i] ? 1 : -1
+		}
+	}
+
+	// Integer parts equal, compare fractional parts
+	max_frac_len := max(len(a_adj.fractional_part), len(b_adj.fractional_part))
+	for i in 0..<max_frac_len {
+		a_digit := i < len(a_adj.fractional_part) ? a_adj.fractional_part[i] : '0'
+		b_digit := i < len(b_adj.fractional_part) ? b_adj.fractional_part[i] : '0'
+
+		if a_digit != b_digit {
+			return a_digit > b_digit ? 1 : -1
+		}
+	}
+
+	return 0
+}
+
+// Adjust a number for its exponent (conceptually multiply by 10^exponent)
+adjust_for_exponent :: proc(num: DDB_Number) -> DDB_Number {
+	if num.exponent == 0 {
+		return num
+	}
+
+	result := num
+	result.exponent = 0
+
+	if num.exponent > 0 {
+		// Shift decimal point right
+		exp := int(num.exponent)
+		frac := num.fractional_part
+
+		// Move fractional digits to integer part
+		shift := min(exp, len(frac))
+		result.integer_part = strings.concatenate({num.integer_part, frac[:shift]})
+		result.fractional_part = frac[shift:]
+
+		// Add zeros if needed
+		if exp > len(frac) {
+			zeros := strings.repeat("0", exp - len(frac))
+			result.integer_part = strings.concatenate({result.integer_part, zeros})
+		}
+	} else {
+		// Shift decimal point left
+		exp := -int(num.exponent)
+		int_part := num.integer_part
+
+		// Move integer digits to fractional part
+		shift := min(exp, len(int_part))
+		result.integer_part = int_part[:len(int_part)-shift]
+		if len(result.integer_part) == 0 {
+			result.integer_part = "0"
+		}
+		result.fractional_part = strings.concatenate({
+			int_part[len(int_part)-shift:],
+			num.fractional_part,
+		})
+
+		// Add leading zeros if needed
+		if exp > len(int_part) {
+			zeros := strings.repeat("0", exp - len(int_part))
+			result.fractional_part = strings.concatenate({zeros, result.fractional_part})
+		}
+	}
+
+	return normalize_ddb_number(result)
+}
+
+// ============================================================================
+// Canonical Encoding for Sort Keys
+//
+// For numbers to sort correctly in byte-wise comparisons, we need a
+// canonical encoding that preserves numeric ordering.
+//
+// Encoding format:
+// - 1 byte: sign/magnitude marker
+//   - 0x00: negative infinity (reserved)
+//   - 0x01-0x7F: negative numbers (inverted magnitude)
+//   - 0x80: zero
+//   - 0x81-0xFE: positive numbers (magnitude)
+//   - 0xFF: positive infinity (reserved)
+// - N bytes: encoded magnitude (variable length)
+//
+// For positive numbers: we encode the magnitude directly with leading byte
+// indicating number of integer digits.
+//
+// For negative numbers: we encode the magnitude inverted (bitwise NOT) so
+// that larger negative numbers sort before smaller ones.
+// ============================================================================
+
+// Encode a DDB_Number into canonical byte form for sort keys
+encode_ddb_number_for_sort :: proc(num: DDB_Number) -> []byte {
+	buf: bytes.Buffer
+	bytes.buffer_init_allocator(&buf, 0, 64, context.allocator)
+
+	if is_ddb_number_zero(num) {
+		bytes.buffer_write_byte(&buf, 0x80)
+		return bytes.buffer_to_bytes(&buf)
+	}
+
+	// Get normalized magnitude
+	norm := normalize_ddb_number(num)
+	adj := adjust_for_exponent(norm)
+
+	// Encode magnitude bytes
+	mag_bytes := encode_magnitude(adj)
+
+	if num.sign {
+		// Positive number: 0x81 + magnitude
+		bytes.buffer_write_byte(&buf, 0x81)
+		bytes.buffer_write(&buf, mag_bytes)
+	} else {
+		// Negative number: 0x7F - inverted magnitude
+		bytes.buffer_write_byte(&buf, 0x7F)
+		// Invert all magnitude bytes
+		for b in mag_bytes {
+			bytes.buffer_write_byte(&buf, ~b)
+		}
+	}
+
+	return bytes.buffer_to_bytes(&buf)
+}
+
+// Encode the magnitude of a number (integer + fractional parts)
+encode_magnitude :: proc(num: DDB_Number) -> []byte {
+	buf: bytes.Buffer
+	bytes.buffer_init_allocator(&buf, 0, 32, context.allocator)
+
+	// Write length of integer part as varint
+	int_len := u64(len(num.integer_part))
+	encode_varint(&buf, int_len)
+
+	// Write integer digits
+	bytes.buffer_write_string(&buf, num.integer_part)
+
+	// Write fractional digits if any
+	if len(num.fractional_part) > 0 {
+		bytes.buffer_write_string(&buf, num.fractional_part)
+	}
+
+	return bytes.buffer_to_bytes(&buf)
+}
+
+// Decode a canonically encoded number back to DDB_Number
+decode_ddb_number_from_sort :: proc(data: []byte) -> (DDB_Number, bool) {
+	if len(data) == 0 {
+		return {}, false
+	}
+
+	marker := data[0]
+
+	// Zero
+	if marker == 0x80 {
+		return DDB_Number{
+			sign = true,
+			integer_part = "0",
+			fractional_part = "",
+			exponent = 0,
+		}, true
+	}
+
+	// Positive number
+	if marker == 0x81 {
+		return decode_magnitude(data[1:], true)
+	}
+
+	// Negative number (inverted bytes)
+	if marker == 0x7F {
+		// Un-invert the bytes
+		inverted := make([]byte, len(data)-1)
+		defer delete(inverted)
+		for i in 0..<len(inverted) {
+			inverted[i] = ~data[i+1]
+		}
+		return decode_magnitude(inverted, false)
+	}
+
+	return {}, false
+}
+
+// Decode magnitude bytes back to a DDB_Number
+decode_magnitude :: proc(data: []byte, positive: bool) -> (DDB_Number, bool) {
+	if len(data) == 0 {
+		return {}, false
+	}
+
+	// Read integer length
+	int_len, bytes_read := decode_varint(data)
+	if bytes_read == 0 || int_len == 0 {
+		return {}, false
+	}
+
+	offset := bytes_read
+
+	// Read integer part
+	if offset + int(int_len) > len(data) {
+		return {}, false
+	}
+	int_part := string(data[offset:offset + int(int_len)])
+	offset += int(int_len)
+
+	// Read fractional part if any
+	frac_part := ""
+	if offset < len(data) {
+		frac_part = string(data[offset:])
+	}
+
+	return DDB_Number{
+		sign = positive,
+		integer_part = int_part,
+		fractional_part = frac_part,
+		exponent = 0,
+	}, true
+}
+
+// ============================================================================
+// Decimal Arithmetic (38-digit precision, no float conversion)
+// ============================================================================
+
+MAX_DDB_PRECISION :: 38
+
+// Add two DDB_Numbers with full decimal precision.
+// Returns an owned DDB_Number.
+add_ddb_numbers :: proc(a: DDB_Number, b: DDB_Number) -> (DDB_Number, bool) {
+	if is_ddb_number_zero(a) { return clone_ddb_number(b), true }
+	if is_ddb_number_zero(b) { return clone_ddb_number(a), true }
+
+	if a.sign == b.sign {
+		// Same sign: add magnitudes, keep sign
+		result, ok := add_magnitudes(a, b)
+		if !ok { return {}, false }
+		result.sign = a.sign
+		return result, true
+	}
+
+	// Different signs: subtract smaller magnitude from larger
+	cmp := compare_ddb_number_magnitudes(a, b)
+	if cmp == 0 {
+		return DDB_Number{
+			sign            = true,
+			integer_part    = strings.clone("0"),
+			fractional_part = strings.clone(""),
+			exponent        = 0,
+		}, true
+	}
+
+	if cmp > 0 {
+		result, ok := subtract_magnitudes(a, b)
+		if !ok { return {}, false }
+		result.sign = a.sign
+		return result, true
+	} else {
+		result, ok := subtract_magnitudes(b, a)
+		if !ok { return {}, false }
+		result.sign = b.sign
+		return result, true
+	}
+}
+
+// Subtract two DDB_Numbers: a - b
+subtract_ddb_numbers :: proc(a: DDB_Number, b: DDB_Number) -> (DDB_Number, bool) {
+	neg_b := b
+	neg_b.sign = !b.sign
+	return add_ddb_numbers(a, neg_b)
+}
+
+// ============================================================================
+// Internal arithmetic helpers
+// ============================================================================
+
+// Expand a DDB_Number to effective integer and fractional digit bytes
+// with the exponent fully applied. Returns heap-allocated slices (caller frees).
+@(private="file")
+expand_digits :: proc(num: DDB_Number) -> (int_digits: []u8, frac_digits: []u8) {
+	dp := len(num.integer_part) + int(num.exponent)
+	all_len := len(num.integer_part) + len(num.fractional_part)
+
+	if dp <= 0 {
+		// Everything is fractional, need leading zeros
+		frac := make([]u8, -dp + all_len)
+		for i in 0..<(-dp) {
+			frac[i] = '0'
+		}
+		for i in 0..<len(num.integer_part) {
+			frac[-dp + i] = num.integer_part[i]
+		}
+		for i in 0..<len(num.fractional_part) {
+			frac[-dp + len(num.integer_part) + i] = num.fractional_part[i]
+		}
+
+		int_d := make([]u8, 1)
+		int_d[0] = '0'
+		return int_d, frac
+	}
+
+	if dp >= all_len {
+		// Everything is integer, may need trailing zeros
+		int_d := make([]u8, dp)
+		for i in 0..<len(num.integer_part) {
+			int_d[i] = num.integer_part[i]
+		}
+		for i in 0..<len(num.fractional_part) {
+			int_d[len(num.integer_part) + i] = num.fractional_part[i]
+		}
+		for i in all_len..<dp {
+			int_d[i] = '0'
+		}
+		return int_d, nil
+	}
+
+	// Decimal point falls within the original integer_part
+	if dp <= len(num.integer_part) {
+		int_d := make([]u8, dp)
+		for i in 0..<dp {
+			int_d[i] = num.integer_part[i]
+		}
+
+		frac_len := (len(num.integer_part) - dp) + len(num.fractional_part)
+		frac := make([]u8, frac_len)
+		for i in dp..<len(num.integer_part) {
+			frac[i - dp] = num.integer_part[i]
+		}
+		offset := len(num.integer_part) - dp
+		for i in 0..<len(num.fractional_part) {
+			frac[offset + i] = num.fractional_part[i]
+		}
+		return int_d, frac
+	}
+
+	// Decimal point falls within the original fractional_part
+	frac_split := dp - len(num.integer_part)
+
+	int_d := make([]u8, dp)
+	for i in 0..<len(num.integer_part) {
+		int_d[i] = num.integer_part[i]
+	}
+	for i in 0..<frac_split {
+		int_d[len(num.integer_part) + i] = num.fractional_part[i]
+	}
+
+	remaining := len(num.fractional_part) - frac_split
+	frac: []u8 = nil
+	if remaining > 0 {
+		frac = make([]u8, remaining)
+		for i in frac_split..<len(num.fractional_part) {
+			frac[i - frac_split] = num.fractional_part[i]
+		}
+	}
+	return int_d, frac
+}
+
+// Normalize a DDB_Number that owns its strings.
+// Clones the trimmed result, frees the originals.
+@(private="file")
+normalize_owned :: proc(num: DDB_Number) -> DDB_Number {
+	norm := normalize_ddb_number(num)
+
+	// Clone the normalized subslices BEFORE freeing originals
+	new_int := strings.clone(norm.integer_part)
+	new_frac := strings.clone(norm.fractional_part)
+
+	// Free the originals
+	delete(num.integer_part)
+	delete(num.fractional_part)
+
+	return DDB_Number{
+		sign            = norm.sign,
+		integer_part    = new_int,
+		fractional_part = new_frac,
+		exponent        = norm.exponent,
+	}
+}
+
+// Add absolute values. Returns owned DDB_Number (sign=true).
+@(private="file")
+add_magnitudes :: proc(a: DDB_Number, b: DDB_Number) -> (DDB_Number, bool) {
+	a_int, a_frac := expand_digits(a)
+	b_int, b_frac := expand_digits(b)
+	defer { delete(a_int); delete(a_frac); delete(b_int); delete(b_frac) }
+
+	max_int  := max(len(a_int), len(b_int))
+	max_frac := max(len(a_frac), len(b_frac))
+	total    := max_int + max_frac
+
+	// Build zero-padded aligned arrays
+	a_aligned := make([]u8, total)
+	b_aligned := make([]u8, total)
+	defer { delete(a_aligned); delete(b_aligned) }
+
+	for i in 0..<total { a_aligned[i] = '0'; b_aligned[i] = '0' }
+
+	// Integer digits: right-aligned in [0..max_int)
+	a_off := max_int - len(a_int)
+	b_off := max_int - len(b_int)
+	for i in 0..<len(a_int) { a_aligned[a_off + i] = a_int[i] }
+	for i in 0..<len(b_int) { b_aligned[b_off + i] = b_int[i] }
+
+	// Fractional digits: left-aligned in [max_int..total)
+	for i in 0..<len(a_frac) { a_aligned[max_int + i] = a_frac[i] }
+	for i in 0..<len(b_frac) { b_aligned[max_int + i] = b_frac[i] }
+
+	// Add right-to-left
+	result := make([]u8, total + 1) // +1 for carry
+	carry: u8 = 0
+	for i := total - 1; i >= 0; i -= 1 {
+		sum := (a_aligned[i] - '0') + (b_aligned[i] - '0') + carry
+		result[i + 1] = (sum % 10) + '0'
+		carry = sum / 10
+	}
+	result[0] = carry + '0'
+
+	// Split: decimal point is at max_int + 1 (carry slot shifts everything)
+	int_end := max_int + 1
+	int_str  := strings.clone(string(result[:int_end]))
+	frac_str := strings.clone(string(result[int_end:]))
+	delete(result)
+
+	num := normalize_owned(DDB_Number{
+		sign            = true,
+		integer_part    = int_str,
+		fractional_part = frac_str,
+		exponent        = 0,
+	})
+
+	if len(num.integer_part) + len(num.fractional_part) > MAX_DDB_PRECISION {
+		delete(num.integer_part)
+		delete(num.fractional_part)
+		return {}, false
+	}
+
+	return num, true
+}
+
+// Subtract absolute values: |a| - |b|, where |a| >= |b|.
+// Returns owned DDB_Number (sign=true).
+@(private="file")
+subtract_magnitudes :: proc(a: DDB_Number, b: DDB_Number) -> (DDB_Number, bool) {
+	a_int, a_frac := expand_digits(a)
+	b_int, b_frac := expand_digits(b)
+	defer { delete(a_int); delete(a_frac); delete(b_int); delete(b_frac) }
+
+	max_int  := max(len(a_int), len(b_int))
+	max_frac := max(len(a_frac), len(b_frac))
+	total    := max_int + max_frac
+
+	a_aligned := make([]u8, total)
+	b_aligned := make([]u8, total)
+	defer { delete(a_aligned); delete(b_aligned) }
+
+	for i in 0..<total { a_aligned[i] = '0'; b_aligned[i] = '0' }
+
+	a_off := max_int - len(a_int)
+	b_off := max_int - len(b_int)
+	for i in 0..<len(a_int) { a_aligned[a_off + i] = a_int[i] }
+	for i in 0..<len(b_int) { b_aligned[b_off + i] = b_int[i] }
+	for i in 0..<len(a_frac) { a_aligned[max_int + i] = a_frac[i] }
+	for i in 0..<len(b_frac) { b_aligned[max_int + i] = b_frac[i] }
+
+	// Subtract right-to-left
+	result := make([]u8, total)
+	borrow: u8 = 0
+	for i := total - 1; i >= 0; i -= 1 {
+		ad := a_aligned[i] - '0'
+		bd := (b_aligned[i] - '0') + borrow
+		if ad < bd {
+			ad += 10
+			borrow = 1
+		} else {
+			borrow = 0
+		}
+		result[i] = (ad - bd) + '0'
+	}
+
+	int_str  := strings.clone(string(result[:max_int]))
+	frac_str := strings.clone(string(result[max_int:]))
+	delete(result)
+
+	if len(int_str) == 0 {
+		delete(int_str)
+		int_str = strings.clone("0")
+	}
+
+	num := normalize_owned(DDB_Number{
+		sign            = true,
+		integer_part    = int_str,
+		fractional_part = frac_str,
+		exponent        = 0,
+	})
+
+	if len(num.integer_part) + len(num.fractional_part) > MAX_DDB_PRECISION {
+		delete(num.integer_part)
+		delete(num.fractional_part)
+		return {}, false
+	}
+
+	return num, true
+}
+
+// Format a DDB_Number for display
+format_ddb_number :: proc(num: DDB_Number) -> string {
+	// Normalize first
+	norm := normalize_ddb_number(num)
+
+	// Check if it's effectively an integer
+	if len(norm.fractional_part) == 0 && norm.exponent >= 0 {
+		builder := strings.builder_make()
+		if !norm.sign {
+			strings.write_string(&builder, "-")
+		}
+		strings.write_string(&builder, norm.integer_part)
+		// Add trailing zeros for positive exponent
+		for _ in 0..<norm.exponent {
+			strings.write_string(&builder, "0")
+		}
+		return strings.to_string(builder)
+	}
+
+	// Otherwise use full representation
+	return ddb_number_to_string(norm)
+}
+
+// Clones a ddb number type
+clone_ddb_number :: proc(num: DDB_Number) -> DDB_Number {
+	return DDB_Number{
+		sign = num.sign,
+		integer_part = strings.clone(num.integer_part),
+		fractional_part = strings.clone(num.fractional_part),
+		exponent = num.exponent,
+	}
+}
+
+// Helper: encode_varint (you already have this in your codebase)
+@(private="file")
+encode_varint :: proc(buf: ^bytes.Buffer, value: u64) {
+	v := value
+	for {
+		byte_val := u8(v & 0x7F)
+		v >>= 7
+		if v != 0 {
+			byte_val |= 0x80
+		}
+		bytes.buffer_write_byte(buf, byte_val)
+		if v == 0 {
+			break
+		}
+	}
+}
+
+// Helper: decode_varint
+@(private="file")
+decode_varint :: proc(data: []byte) -> (value: u64, bytes_read: int) {
+	shift: u64 = 0
+	for i in 0..<len(data) {
+		byte_val := data[i]
+		value |= u64(byte_val & 0x7F) << shift
+		bytes_read = i + 1
+		if (byte_val & 0x80) == 0 {
+			return
+		}
+		shift += 7
+	}
+	return 0, 0
+}

dynamodb/storage.odin

@@ -22,6 +22,9 @@ Storage_Error :: enum {
 	Serialization_Error,
 	RocksDB_Error,
 	Out_Of_Memory,
+	Validation_Error,
+	Request_Too_Large,
+	Internal_Error,
 }
 
 // Result type for Scan operations with pagination
@@ -84,7 +87,23 @@ table_metadata_destroy :: proc(metadata: ^Table_Metadata, allocator: mem.Allocat
 	}
 	delete(metadata.attribute_definitions, allocator)
 
-	// TODO: Free GSI/LSI if we implement them
+	// Free GSI definitions
+	if gsis, has_gsis := metadata.global_secondary_indexes.?; has_gsis {
+		for gsi in gsis {
+			delete(gsi.index_name, allocator)
+			for ks in gsi.key_schema {
+				delete(ks.attribute_name, allocator)
+			}
+			delete(gsi.key_schema, allocator)
+			if nka, has_nka := gsi.projection.non_key_attributes.?; has_nka {
+				for attr in nka {
+					delete(attr, allocator)
+				}
+				delete(nka, allocator)
+			}
+		}
+		delete(gsis, allocator)
+	}
 }
 
 // Get the partition key attribute name
@@ -174,10 +193,14 @@ remove_table_lock :: proc(engine: ^Storage_Engine, table_name: string) {
 	sync.mutex_lock(&engine.table_locks_mutex)
 	defer sync.mutex_unlock(&engine.table_locks_mutex)
 
-	if lock, found := engine.table_locks[table_name]; found {
+	// Find the actual heap-allocated key string from the map
-		delete(table_name, engine.allocator)
+	for key, lock in engine.table_locks {
-		free(lock, engine.allocator)
+		if key == table_name {
-		delete_key(&engine.table_locks, table_name)
+			delete_key(&engine.table_locks, key)
+			delete(key, engine.allocator) // free the map's owned key!
+			free(lock, engine.allocator)
+			break
+		}
 	}
 }
 
@@ -187,7 +210,6 @@ remove_table_lock :: proc(engine: ^Storage_Engine, table_name: string) {
 
 // Serialize table metadata to binary format
 serialize_table_metadata :: proc(metadata: ^Table_Metadata) -> ([]byte, bool) {
-	// Create a temporary item to hold metadata
 	meta_item := make(Item, context.temp_allocator)
 	defer delete(meta_item)
 
@@ -200,7 +222,7 @@ serialize_table_metadata :: proc(metadata: ^Table_Metadata) -> ([]byte, bool) {
 		if i > 0 {
 			strings.write_string(&ks_builder, ",")
 		}
-		fmt.sbprintf(&ks_builder, `{"AttributeName":"%s","KeyType":"%s"}`,
+		fmt.sbprintf(&ks_builder, `{{"AttributeName":"%s","KeyType":"%s"}}`,
 			ks.attribute_name, key_type_to_string(ks.key_type))
 	}
 	strings.write_string(&ks_builder, "]")
@@ -216,7 +238,7 @@ serialize_table_metadata :: proc(metadata: ^Table_Metadata) -> ([]byte, bool) {
 		if i > 0 {
 			strings.write_string(&ad_builder, ",")
 		}
-		fmt.sbprintf(&ad_builder, `{"AttributeName":"%s","AttributeType":"%s"}`,
+		fmt.sbprintf(&ad_builder, `{{"AttributeName":"%s","AttributeType":"%s"}}`,
 			ad.attribute_name, scalar_type_to_string(ad.attribute_type))
 	}
 	strings.write_string(&ad_builder, "]")
@@ -225,7 +247,55 @@ serialize_table_metadata :: proc(metadata: ^Table_Metadata) -> ([]byte, bool) {
 
 	// Add other metadata
 	meta_item["TableStatus"] = String(strings.clone(table_status_to_string(metadata.table_status)))
-	meta_item["CreationDateTime"] = Number(fmt.aprint(metadata.creation_date_time))
+	ts_str := fmt.aprint(metadata.creation_date_time)
+	ts_num, ts_ok := parse_ddb_number(ts_str)
+	if ts_ok {
+		meta_item["CreationDateTime"] = ts_num
+	} else {
+		meta_item["CreationDateTime"] = String(strings.clone(ts_str))
+	}
+
+	// Encode GSI definitions as JSON string
+	if gsis, has_gsis := metadata.global_secondary_indexes.?; has_gsis && len(gsis) > 0 {
+		gsi_builder := strings.builder_make(context.temp_allocator)
+		defer strings.builder_destroy(&gsi_builder)
+
+		strings.write_string(&gsi_builder, "[")
+		for gsi, i in gsis {
+			if i > 0 {
+				strings.write_string(&gsi_builder, ",")
+			}
+			fmt.sbprintf(&gsi_builder, `{{"IndexName":"%s","KeySchema":[`, gsi.index_name)
+			for ks, j in gsi.key_schema {
+				if j > 0 {
+					strings.write_string(&gsi_builder, ",")
+				}
+				fmt.sbprintf(&gsi_builder, `{{"AttributeName":"%s","KeyType":"%s"}}`,
+					ks.attribute_name, key_type_to_string(ks.key_type))
+			}
+			strings.write_string(&gsi_builder, `],"Projection":{"ProjectionType":"`)
+			switch gsi.projection.projection_type {
+			case .ALL:       strings.write_string(&gsi_builder, "ALL")
+			case .KEYS_ONLY: strings.write_string(&gsi_builder, "KEYS_ONLY")
+			case .INCLUDE:   strings.write_string(&gsi_builder, "INCLUDE")
+			}
+			strings.write_string(&gsi_builder, `"`)
+			if nka, has_nka := gsi.projection.non_key_attributes.?; has_nka && len(nka) > 0 {
+				strings.write_string(&gsi_builder, `,"NonKeyAttributes":[`)
+				for attr, k in nka {
+					if k > 0 {
+						strings.write_string(&gsi_builder, ",")
+					}
+					fmt.sbprintf(&gsi_builder, `"%s"`, attr)
+				}
+				strings.write_string(&gsi_builder, "]")
+			}
+			strings.write_string(&gsi_builder, "}}")
+		}
+		strings.write_string(&gsi_builder, "]")
+
+		meta_item["GlobalSecondaryIndexes"] = String(strings.clone(strings.to_string(gsi_builder)))
+	}
 
 	// Encode to binary
 	return encode(meta_item)
@@ -254,8 +324,9 @@ deserialize_table_metadata :: proc(data: []byte, allocator: mem.Allocator) -> (T
 	// Parse creation date time
 	if time_val, found := meta_item["CreationDateTime"]; found {
 		#partial switch v in time_val {
-		case Number:
+		case DDB_Number:
-			val, parse_ok := strconv.parse_i64(string(v))
+			num_str := format_ddb_number(v)
+			val, parse_ok := strconv.parse_i64(num_str)
 			metadata.creation_date_time = val if parse_ok else 0
 		}
 	}
@@ -282,6 +353,17 @@ deserialize_table_metadata :: proc(data: []byte, allocator: mem.Allocator) -> (T
 		}
 	}
 
+	// Parse GlobalSecondaryIndexes from embedded JSON string
+	if gsi_val, gsi_found := meta_item["GlobalSecondaryIndexes"]; gsi_found {
+		#partial switch v in gsi_val {
+		case String:
+			gsis, gsi_ok := parse_gsis_json(string(v), allocator)
+			if gsi_ok && len(gsis) > 0 {
+				metadata.global_secondary_indexes = gsis
+			}
+		}
+	}
+
 	return metadata, true
 }
 
@@ -450,6 +532,10 @@ get_table_metadata :: proc(engine: ^Storage_Engine, table_name: string) -> (Tabl
 		return {}, .Serialization_Error
 	}
 
+	// table_name is not stored in the serialized blob (it IS the RocksDB key),
+	// so we populate it here from the argument we already have.
+	metadata.table_name = strings.clone(table_name, engine.allocator)
+
 	return metadata, .None
 }
 
@@ -463,6 +549,7 @@ create_table :: proc(
 	table_name: string,
 	key_schema: []Key_Schema_Element,
 	attribute_definitions: []Attribute_Definition,
+	gsis: Maybe([]Global_Secondary_Index) = nil,
 ) -> (Table_Description, Storage_Error) {
 	table_lock := get_or_create_table_lock(engine, table_name)
 	sync.rw_mutex_lock(table_lock)
@@ -500,6 +587,34 @@ create_table :: proc(
 		ad.attribute_name = strings.clone(ad.attribute_name, engine.allocator)
 	}
 
+	// Deep copy GSI definitions into engine allocator
+	if gsi_defs, has_gsis := gsis.?; has_gsis && len(gsi_defs) > 0 {
+		owned_gsis := make([]Global_Secondary_Index, len(gsi_defs), engine.allocator)
+		for gsi_def, i in gsi_defs {
+			owned_gsis[i] = Global_Secondary_Index{
+				index_name = strings.clone(gsi_def.index_name, engine.allocator),
+				key_schema = make([]Key_Schema_Element, len(gsi_def.key_schema), engine.allocator),
+				projection = Projection{
+					projection_type = gsi_def.projection.projection_type,
+				},
+			}
+			for ks, j in gsi_def.key_schema {
+				owned_gsis[i].key_schema[j] = Key_Schema_Element{
+					attribute_name = strings.clone(ks.attribute_name, engine.allocator),
+					key_type = ks.key_type,
+				}
+			}
+			if nka, has_nka := gsi_def.projection.non_key_attributes.?; has_nka {
+				owned_nka := make([]string, len(nka), engine.allocator)
+				for attr, k in nka {
+					owned_nka[k] = strings.clone(attr, engine.allocator)
+				}
+				owned_gsis[i].projection.non_key_attributes = owned_nka
+			}
+		}
+		metadata.global_secondary_indexes = owned_gsis
+	}
+
 	// Serialize and store
 	meta_value, serialize_ok := serialize_table_metadata(&metadata)
 	if !serialize_ok {
@@ -522,6 +637,7 @@ create_table :: proc(
 		creation_date_time = now,
 		item_count = 0,
 		table_size_bytes = 0,
+		global_secondary_indexes = gsis,
 	}
 
 	return desc, .None
@@ -565,7 +681,6 @@ delete_table :: proc(engine: ^Storage_Engine, table_name: string) -> Storage_Err
 				break
 			}
 
-			// Delete this item
 			err: cstring
 			rocksdb.rocksdb_delete(
 				engine.db.handle,
@@ -582,6 +697,41 @@ delete_table :: proc(engine: ^Storage_Engine, table_name: string) -> Storage_Err
 		}
 	}
 
+	// Delete all GSI entries for this table
+	gsi_table_prefix := build_gsi_table_prefix(table_name)
+	defer delete(gsi_table_prefix)
+
+	gsi_iter := rocksdb.rocksdb_create_iterator(engine.db.handle, engine.db.read_options)
+	if gsi_iter != nil {
+		defer rocksdb.rocksdb_iter_destroy(gsi_iter)
+
+		rocksdb.rocksdb_iter_seek(gsi_iter, raw_data(gsi_table_prefix), c.size_t(len(gsi_table_prefix)))
+
+		for rocksdb.rocksdb_iter_valid(gsi_iter) != 0 {
+			key_len: c.size_t
+			key_ptr := rocksdb.rocksdb_iter_key(gsi_iter, &key_len)
+			key_bytes := key_ptr[:key_len]
+
+			if !has_prefix(key_bytes, gsi_table_prefix) {
+				break
+			}
+
+			err: cstring
+			rocksdb.rocksdb_delete(
+				engine.db.handle,
+				engine.db.write_options,
+				raw_data(key_bytes),
+				c.size_t(len(key_bytes)),
+				&err,
+			)
+			if err != nil {
+				rocksdb.rocksdb_free(rawptr(err))
+			}
+
+			rocksdb.rocksdb_iter_next(gsi_iter)
+		}
+	}
+
 	// Delete metadata
 	del_err := rocksdb.db_delete(&engine.db, meta_key)
 	if del_err != .None {
@@ -597,6 +747,7 @@ delete_table :: proc(engine: ^Storage_Engine, table_name: string) -> Storage_Err
 // ============================================================================
 
 // Put item — uses EXCLUSIVE lock (write operation)
+// ATOMICITY: Uses WriteBatch to ensure base item + all GSI updates are atomic
 put_item :: proc(engine: ^Storage_Engine, table_name: string, item: Item) -> Storage_Error {
 	table_lock := get_or_create_table_lock(engine, table_name)
 	sync.rw_mutex_lock(table_lock)
@@ -639,16 +790,66 @@ put_item :: proc(engine: ^Storage_Engine, table_name: string, item: Item) -> Sto
 	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
 	defer delete(storage_key)
 
-	// Encode item
+	// --- Check if item already exists (need old item for GSI cleanup) ---
+	old_item: Maybe(Item) = nil
+	existing_value, existing_err := rocksdb.db_get(&engine.db, storage_key)
+	if existing_err == .NotFound {
+		// Item does not exist — nothing to clean up, proceed normally.
+	} else if existing_err != .None {
+		// Unexpected RocksDB I/O error — fail closed to avoid orphaned GSI entries.
+		return .RocksDB_Error
+	} else if existing_value != nil {
+		defer delete(existing_value)
+		decoded_old, decode_ok := decode(existing_value)
+		if !decode_ok {
+			// Value exists but is unreadable — fail closed rather than leaving
+			// stale GSI entries behind after the overwrite.
+			return .Serialization_Error
+		}
+		old_item = decoded_old
+	}
+	// Cleanup old_item at the end
+	defer {
+		if old, has_old := old_item.?; has_old {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+	}
+
+	// Encode new item
 	encoded_item, encode_ok := encode(item)
 	if !encode_ok {
 		return .Serialization_Error
 	}
 	defer delete(encoded_item)
 
-	// Store in RocksDB
+	// --- ATOMIC WRITE BATCH: base item + all GSI updates ---
-	put_err := rocksdb.db_put(&engine.db, storage_key, encoded_item)
+	batch, batch_err := rocksdb.batch_create()
-	if put_err != .None {
+	if batch_err != .None {
+		return .RocksDB_Error
+	}
+	defer rocksdb.batch_destroy(&batch)
+
+	// Add base item write to batch
+	rocksdb.batch_put(&batch, storage_key, encoded_item)
+
+	// Add old GSI entry deletions to batch (if item existed)
+	if old, has_old := old_item.?; has_old {
+		gsi_del_err := gsi_batch_delete_entries(&batch, table_name, old, &metadata)
+		if gsi_del_err != .None {
+			return gsi_del_err
+		}
+	}
+
+	// Add new GSI entry writes to batch
+	gsi_write_err := gsi_batch_write_entries(&batch, table_name, item, &metadata)
+	if gsi_write_err != .None {
+		return gsi_write_err
+	}
+
+	// Write batch atomically - ALL or NOTHING
+	write_err := rocksdb.batch_write(&engine.db, &batch)
+	if write_err != .None {
 		return .RocksDB_Error
 	}
 
@@ -712,6 +913,7 @@ get_item :: proc(engine: ^Storage_Engine, table_name: string, key: Item) -> (May
 }
 
 // Delete item — uses EXCLUSIVE lock (write operation)
+// ATOMICITY: Uses WriteBatch to ensure base item + all GSI deletions are atomic
 delete_item :: proc(engine: ^Storage_Engine, table_name: string, key: Item) -> Storage_Error {
 	table_lock := get_or_create_table_lock(engine, table_name)
 	sync.rw_mutex_lock(table_lock)
@@ -748,9 +950,59 @@ delete_item :: proc(engine: ^Storage_Engine, table_name: string, key: Item) -> S
 	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
 	defer delete(storage_key)
 
-	// Delete from RocksDB
+	// --- Read existing item to know which GSI entries to remove ---
-	del_err := rocksdb.db_delete(&engine.db, storage_key)
+	old_item: Maybe(Item) = nil
-	if del_err != .None {
+	existing_value, existing_err := rocksdb.db_get(&engine.db, storage_key)
+	if existing_err == .NotFound {
+		// Item does not exist — nothing to delete (DynamoDB idempotent delete).
+		return .None
+	} else if existing_err != .None {
+		// Unexpected RocksDB I/O error — fail closed.
+		return .RocksDB_Error
+	} else if existing_value != nil {
+		defer delete(existing_value)
+		decoded_old, decode_ok := decode(existing_value)
+		if !decode_ok {
+			// Value exists but is corrupt — fail closed rather than deleting the
+			// base item while leaving its GSI entries dangling.
+			return .Serialization_Error
+		}
+		old_item = decoded_old
+	}
+	// Cleanup old_item at the end
+	defer {
+		if old, has_old := old_item.?; has_old {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+	}
+
+	// If item doesn't exist (existing_value was nil with no error), nothing to delete.
+	if _, has_old := old_item.?; !has_old {
+		return .None
+	}
+
+	// --- ATOMIC WRITE BATCH: base item deletion + all GSI deletions ---
+	batch, batch_err := rocksdb.batch_create()
+	if batch_err != .None {
+		return .RocksDB_Error
+	}
+	defer rocksdb.batch_destroy(&batch)
+
+	// Add base item delete to batch
+	rocksdb.batch_delete(&batch, storage_key)
+
+	// Add GSI entry deletions to batch
+	if old, has_old := old_item.?; has_old {
+		gsi_del_err := gsi_batch_delete_entries(&batch, table_name, old, &metadata)
+		if gsi_del_err != .None {
+			return gsi_del_err
+		}
+	}
+
+	// Write batch atomically - ALL or NOTHING
+	write_err := rocksdb.batch_write(&engine.db, &batch)
+	if write_err != .None {
 		return .RocksDB_Error
 	}
 
@@ -1006,6 +1258,43 @@ evaluate_sort_key_condition :: proc(item: Item, skc: ^Sort_Key_Condition) -> boo
 		return false
 	}
 
+	// Use numeric comparison if both sides are DDB_Number
+	item_num, item_is_num := attr.(DDB_Number)
+	cond_num, cond_is_num := skc.value.(DDB_Number)
+
+	if item_is_num && cond_is_num {
+		cmp := compare_ddb_numbers(item_num, cond_num)
+
+		switch skc.operator {
+		case .EQ:
+			return cmp == 0
+		case .LT:
+			return cmp < 0
+		case .LE:
+			return cmp <= 0
+		case .GT:
+			return cmp > 0
+		case .GE:
+			return cmp >= 0
+		case .BETWEEN:
+			if v2, has_v2 := skc.value2.?; has_v2 {
+				upper_num, upper_ok := v2.(DDB_Number)
+				if !upper_ok {
+					return false
+				}
+				cmp2 := compare_ddb_numbers(item_num, upper_num)
+				return cmp >= 0 && cmp2 <= 0
+			}
+			return false
+		case .BEGINS_WITH:
+			// begins_with is not a valid operator for Number sort keys.
+			// DynamoDB rejects this at validation time. Return false.
+			return false
+		}
+		return false
+	}
+
+	// Fallback: string comparison for S/B types
 	item_sk_str, ok1 := attr_value_to_string_for_compare(attr)
 	if !ok1 {
 		return false
@@ -1047,13 +1336,15 @@ evaluate_sort_key_condition :: proc(item: Item, skc: ^Sort_Key_Condition) -> boo
 }
 
 // Extract a comparable string from a scalar AttributeValue
-@(private = "file")
+// Package-visible: used by filter.odin for comparisons
 attr_value_to_string_for_compare :: proc(attr: Attribute_Value) -> (string, bool) {
 	#partial switch v in attr {
 	case String:
 		return string(v), true
-	case Number:
+	case DDB_Number:
-		return string(v), true
+		// Return formatted string for fallback string comparison
+		// (actual numeric comparison is handled in compare_attribute_values)
+		return format_ddb_number(v), true
 	case Binary:
 		return string(v), true
 	}
@@ -1098,7 +1389,7 @@ validate_item_key_types :: proc(
 		#partial switch _ in attr {
 		case String:
 			match = (et == .S)
-		case Number:
+		case DDB_Number:
 			match = (et == .N)
 		case Binary:
 			match = (et == .B)

dynamodb/transact.odin

@@ -0,0 +1,813 @@
+// TransactWriteItems and TransactGetItems storage operations
+//
+// TransactWriteItems: Atomic write of up to 100 items across multiple tables.
+//   - Supports Put, Delete, Update, and ConditionCheck actions
+//   - ALL actions succeed or ALL fail (all-or-nothing)
+//   - ConditionExpressions are evaluated BEFORE any mutations
+//   - Uses exclusive locks on all involved tables
+//
+// TransactGetItems: Atomic read of up to 100 items across multiple tables.
+//   - Each item specifies TableName + Key + optional ProjectionExpression
+//   - All reads are consistent (snapshot isolation via table locks)
+package dynamodb
+
+import "core:strings"
+import "core:sync"
+import "../rocksdb"
+
+// ============================================================================
+// TransactWriteItems Types
+// ============================================================================
+
+Transact_Write_Action_Type :: enum {
+	Put,
+	Delete,
+	Update,
+	Condition_Check,
+}
+
+Transact_Write_Action :: struct {
+	type:                Transact_Write_Action_Type,
+	table_name:          string,
+	// For Put: the full item to write
+	item:                Maybe(Item),
+	// For Delete/Update/ConditionCheck: the key item
+	key:                 Maybe(Item),
+	// For Update: the parsed update plan
+	update_plan:         Maybe(Update_Plan),
+	// ConditionExpression components (shared across all action types)
+	condition_expr:      Maybe(string),
+	expr_attr_names:     Maybe(map[string]string),
+	expr_attr_values:    map[string]Attribute_Value,
+	// For Update: ReturnValuesOnConditionCheckFailure (not implemented yet, placeholder)
+}
+
+Transact_Write_Result :: struct {
+	// For now, either all succeed (no error) or we return a
+	// TransactionCanceledException with reasons per action.
+	cancellation_reasons: []Cancellation_Reason,
+}
+
+Cancellation_Reason :: struct {
+	code:    string, // "None", "ConditionalCheckFailed", "ValidationError", etc.
+	message: string,
+}
+
+transact_write_action_destroy :: proc(action: ^Transact_Write_Action) {
+	delete(action.table_name)
+	if ce, has := action.condition_expr.?; has {
+		delete(ce)
+	}
+	if item, has := action.item.?; has {
+		item_copy := item
+		item_destroy(&item_copy)
+	}
+	if key, has := action.key.?; has {
+		key_copy := key
+		item_destroy(&key_copy)
+	}
+	if plan, has := action.update_plan.?; has {
+		plan_copy := plan
+		update_plan_destroy(&plan_copy)
+	}
+	if names, has := action.expr_attr_names.?; has {
+		for k, v in names {
+			delete(k)
+			delete(v)
+		}
+		names_copy := names
+		delete(names_copy)
+	}
+	for k, v in action.expr_attr_values {
+		delete(k)
+		v_copy := v
+		attr_value_destroy(&v_copy)
+	}
+	delete(action.expr_attr_values)
+}
+
+transact_write_result_destroy :: proc(result: ^Transact_Write_Result) {
+	if result.cancellation_reasons != nil {
+		delete(result.cancellation_reasons)
+	}
+}
+
+// ============================================================================
+// TransactWriteItems — Execute an atomic batch of write operations
+//
+// DynamoDB semantics:
+//   1. Acquire exclusive locks on all involved tables
+//   2. Evaluate ALL ConditionExpressions (pre-flight check)
+//   3. If any condition fails → cancel entire transaction
+//   4. If all pass → apply all mutations
+//   5. Release locks
+//
+// Returns .None on success, Transaction_Cancelled on condition failure.
+// ============================================================================
+
+Transaction_Error :: enum {
+	None,
+	Cancelled,               // One or more conditions failed
+	Validation_Error,        // Bad request data
+	Internal_Error,          // Storage/serialization failure
+}
+
+transact_write_items :: proc(
+	engine: ^Storage_Engine,
+	actions: []Transact_Write_Action,
+) -> (Transact_Write_Result, Transaction_Error) {
+	result: Transact_Write_Result
+
+	if len(actions) == 0 {
+		return result, .Validation_Error
+	}
+
+	// ---- Step 1: Collect unique table names and acquire locks ----
+	table_set := make(map[string]bool, allocator = context.temp_allocator)
+	for action in actions {
+		table_set[action.table_name] = true
+	}
+
+	table_names := make([dynamic]string, allocator = context.temp_allocator)
+	for name in table_set {
+		append(&table_names, name)
+	}
+	// Sort for deterministic lock ordering
+	for i := 0; i < len(table_names); i += 1 {
+		for j := i + 1; j < len(table_names); j += 1 {
+			if table_names[j] < table_names[i] {
+				table_names[i], table_names[j] = table_names[j], table_names[i]
+			}
+		}
+	}
+
+	locks := make([dynamic]^sync.RW_Mutex, allocator = context.temp_allocator)
+	for name in table_names {
+		lock := get_or_create_table_lock(engine, name)
+		sync.rw_mutex_lock(lock)
+		append(&locks, lock)
+	}
+	defer {
+		for i := len(locks) - 1; i >= 0; i -= 1 {
+			sync.rw_mutex_unlock(locks[i])
+		}
+	}
+
+	// ---- Step 2: Fetch metadata and evaluate conditions ----
+	reasons := make([]Cancellation_Reason, len(actions))
+	any_failed := false
+
+	metadata_cache := make(map[string]Table_Metadata, allocator = context.temp_allocator)
+	defer {
+		for _, meta in metadata_cache {
+			meta_copy := meta
+			table_metadata_destroy(&meta_copy, engine.allocator)
+		}
+	}
+
+	for action, idx in actions {
+		metadata: ^Table_Metadata
+		if cached, found := &metadata_cache[action.table_name]; found {
+			metadata = cached
+		} else {
+			meta, meta_err := get_table_metadata(engine, action.table_name)
+			if meta_err != .None {
+				reasons[idx] = Cancellation_Reason{
+					code    = "ValidationError",
+					message = "Table not found",
+				}
+				any_failed = true
+				continue
+			}
+			metadata_cache[action.table_name] = meta
+			metadata = &metadata_cache[action.table_name]
+		}
+
+		key_item: Item
+		switch action.type {
+		case .Put:
+			if item, has := action.item.?; has {
+				key_item = item
+			} else {
+				reasons[idx] = Cancellation_Reason{
+					code    = "ValidationError",
+					message = "Put action missing Item",
+				}
+				any_failed = true
+				continue
+			}
+		case .Delete, .Update, .Condition_Check:
+			if key, has := action.key.?; has {
+				key_item = key
+			} else {
+				reasons[idx] = Cancellation_Reason{
+					code    = "ValidationError",
+					message = "Action missing Key",
+				}
+				any_failed = true
+				continue
+			}
+		}
+
+		// Evaluate ConditionExpression
+		if cond_str, has_cond := action.condition_expr.?; has_cond {
+			existing_item, get_err := get_item_internal(engine, action.table_name, key_item, metadata)
+			if get_err != .None && get_err != .Item_Not_Found {
+				reasons[idx] = Cancellation_Reason{
+					code    = "InternalError",
+					message = "Failed to read existing item",
+				}
+				any_failed = true
+				continue
+			}
+			defer {
+				if ex, has_ex := existing_item.?; has_ex {
+					ex_copy := ex
+					item_destroy(&ex_copy)
+				}
+			}
+
+			filter_node, parse_ok := parse_filter_expression(
+				cond_str, action.expr_attr_names, action.expr_attr_values,
+			)
+			if !parse_ok || filter_node == nil {
+				reasons[idx] = Cancellation_Reason{
+					code    = "ValidationError",
+					message = "Invalid ConditionExpression",
+				}
+				any_failed = true
+				continue
+			}
+			defer {
+				filter_node_destroy(filter_node)
+			}
+
+			eval_item: Item
+			if item, has_item := existing_item.?; has_item {
+				eval_item = item
+			} else {
+				eval_item = Item{}
+			}
+
+			if !evaluate_filter(eval_item, filter_node) {
+				reasons[idx] = Cancellation_Reason{
+					code    = "ConditionalCheckFailed",
+					message = "The conditional request failed",
+				}
+				any_failed = true
+				continue
+			}
+		}
+
+		if action.type == .Condition_Check {
+			reasons[idx] = Cancellation_Reason{code = "None"}
+			continue
+		}
+
+		// Validate key/item
+		switch action.type {
+		case .Put:
+			if item, has := action.item.?; has {
+				validation_err := validate_item_key_types(
+					item, metadata.key_schema, metadata.attribute_definitions,
+				)
+				if validation_err != .None {
+					reasons[idx] = Cancellation_Reason{
+						code    = "ValidationError",
+						message = "Key attribute type mismatch",
+					}
+					any_failed = true
+					continue
+				}
+			}
+		case .Delete, .Update:
+			// Key validation happens during batch building
+		case .Condition_Check:
+			// Already handled
+		}
+
+		reasons[idx] = Cancellation_Reason{code = "None"}
+	}
+
+	if any_failed {
+		result.cancellation_reasons = reasons
+		return result, .Cancelled
+	}
+
+	// ---- Step 3: Build atomic WriteBatch with all operations ----
+	batch, batch_err := rocksdb.batch_create()
+	if batch_err != .None {
+		result.cancellation_reasons = reasons
+		return result, .Internal_Error
+	}
+	defer rocksdb.batch_destroy(&batch)
+
+	// Read old items for GSI cleanup (must happen before batch write)
+	old_items := make([]Maybe(Item), len(actions), allocator = context.temp_allocator)
+	defer {
+		for old_item in old_items {
+			if old, has := old_item.?; has {
+				old_copy := old
+				item_destroy(&old_copy)
+			}
+		}
+	}
+
+	for action, idx in actions {
+		if action.type == .Condition_Check {
+			continue
+		}
+
+		metadata := &metadata_cache[action.table_name]
+
+		// Read old item if needed for GSI cleanup
+		key_item: Item
+		#partial switch action.type {
+		case .Put:
+			if item, has := action.item.?; has {
+				key_item = item
+			}
+		case .Delete, .Update:
+			if key, has := action.key.?; has {
+				key_item = key
+			}
+		}
+
+		existing, read_err := get_item_internal(engine, action.table_name, key_item, metadata)
+		#partial switch read_err {
+			case .None:
+				// Item found or not found — both fine.
+			case .RocksDB_Error, .Serialization_Error, .Internal_Error:
+				// Cannot safely determine old index keys — cancel the entire transaction.
+				reasons[idx] = Cancellation_Reason{
+					code    = "InternalError",
+					message = "Failed to read existing item for index maintenance",
+				}
+				result.cancellation_reasons = reasons
+				return result, .Internal_Error
+			case .Missing_Key_Attribute, .Invalid_Key:
+				// The key we built from the action's own item/key should always be valid
+				// by this point (validated earlier), but treat defensively.
+				reasons[idx] = Cancellation_Reason{
+					code    = "ValidationError",
+					message = "Invalid key when reading existing item",
+				}
+				result.cancellation_reasons = reasons
+				return result, .Internal_Error
+			case .Table_Not_Found, .Item_Not_Found, .Validation_Error:
+				// These should not be returned by get_item_internal, but handle
+				// defensively — treat as "item does not exist" and continue.
+		}
+		old_items[idx] = existing
+	}
+
+	// Add all operations to batch
+	for &action, idx in actions {
+		if action.type == .Condition_Check {
+			continue
+		}
+
+		metadata := &metadata_cache[action.table_name]
+		old_item := old_items[idx]
+
+		apply_err := transact_apply_action_batch(&batch, engine, &action, metadata, old_item)
+		if apply_err != .None {
+			reasons[idx] = Cancellation_Reason{
+				code    = "InternalError",
+				message = "Failed to build mutation",
+			}
+			result.cancellation_reasons = reasons
+			return result, .Internal_Error
+		}
+	}
+
+	// ---- Step 4: Write batch atomically (ALL or NOTHING) ----
+	write_err := rocksdb.batch_write(&engine.db, &batch)
+	if write_err != .None {
+		result.cancellation_reasons = reasons
+		return result, .Internal_Error
+	}
+
+	delete(reasons)
+	return result, .None
+}
+
+// Apply a single transact write action (called after all conditions have passed)
+@(private = "file")
+transact_apply_action_batch :: proc(
+	batch: ^rocksdb.WriteBatch,
+	engine: ^Storage_Engine,
+	action: ^Transact_Write_Action,
+	metadata: ^Table_Metadata,
+	old_item: Maybe(Item),
+) -> Storage_Error {
+	switch action.type {
+	case .Put:
+		if item, has := action.item.?; has {
+			return put_item_batch(batch, engine, action.table_name, item, metadata, old_item)
+		}
+		return .Invalid_Key
+
+	case .Delete:
+		if key, has := action.key.?; has {
+			return delete_item_batch(batch, engine, action.table_name, key, metadata, old_item)
+		}
+		return .Invalid_Key
+
+	case .Update:
+		if key, has := action.key.?; has {
+			if plan, has_plan := action.update_plan.?; has_plan {
+				plan_copy := plan
+				return update_item_batch(batch, engine, action.table_name, key, &plan_copy, metadata, old_item)
+			}
+			return .Invalid_Key
+		}
+		return .Invalid_Key
+
+	case .Condition_Check:
+		return .None
+	}
+	return .None
+}
+
+@(private = "file")
+put_item_batch :: proc(
+	batch: ^rocksdb.WriteBatch,
+	engine: ^Storage_Engine,
+	table_name: string,
+	item: Item,
+	metadata: ^Table_Metadata,
+	old_item: Maybe(Item),
+) -> Storage_Error {
+	key_struct, key_ok := key_from_item(item, metadata.key_schema)
+	if !key_ok {
+		return .Missing_Key_Attribute
+	}
+	defer key_destroy(&key_struct)
+
+	key_values, kv_ok := key_get_values(&key_struct)
+	if !kv_ok {
+		return .Invalid_Key
+	}
+
+	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
+	defer delete(storage_key)
+
+	encoded_item, encode_ok := encode(item)
+	if !encode_ok {
+		return .Serialization_Error
+	}
+	defer delete(encoded_item)
+
+	// Add base item to batch
+	rocksdb.batch_put(batch, storage_key, encoded_item)
+
+	// Add old GSI deletions to batch
+	if old, has_old := old_item.?; has_old {
+		gsi_del_err := gsi_batch_delete_entries(batch, table_name, old, metadata)
+		if gsi_del_err != .None {
+			return gsi_del_err
+		}
+	}
+
+	// Add new GSI writes to batch
+	gsi_write_err := gsi_batch_write_entries(batch, table_name, item, metadata)
+	if gsi_write_err != .None {
+		return gsi_write_err
+	}
+
+	return .None
+}
+
+// Add delete operation to batch (with GSI cleanup)
+@(private = "file")
+delete_item_batch :: proc(
+	batch: ^rocksdb.WriteBatch,
+	engine: ^Storage_Engine,
+	table_name: string,
+	key: Item,
+	metadata: ^Table_Metadata,
+	old_item: Maybe(Item),
+) -> Storage_Error {
+	key_struct, key_ok := key_from_item(key, metadata.key_schema)
+	if !key_ok {
+		return .Missing_Key_Attribute
+	}
+	defer key_destroy(&key_struct)
+
+	key_values, kv_ok := key_get_values(&key_struct)
+	if !kv_ok {
+		return .Invalid_Key
+	}
+
+	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
+	defer delete(storage_key)
+
+	// Add base item delete to batch
+	rocksdb.batch_delete(batch, storage_key)
+
+	// Add GSI deletions to batch
+	if old, has_old := old_item.?; has_old {
+		gsi_del_err := gsi_batch_delete_entries(batch, table_name, old, metadata)
+		if gsi_del_err != .None {
+			return gsi_del_err
+		}
+	}
+
+	return .None
+}
+
+// Add update operation to batch (with GSI maintenance)
+@(private = "file")
+update_item_batch :: proc(
+	batch: ^rocksdb.WriteBatch,
+	engine: ^Storage_Engine,
+	table_name: string,
+	key_item: Item,
+	plan: ^Update_Plan,
+	metadata: ^Table_Metadata,
+	old_item_pre: Maybe(Item),
+) -> Storage_Error {
+	key_struct, key_ok := key_from_item(key_item, metadata.key_schema)
+	if !key_ok {
+		return .Missing_Key_Attribute
+	}
+	defer key_destroy(&key_struct)
+
+	key_values, kv_ok := key_get_values(&key_struct)
+	if !kv_ok {
+		return .Invalid_Key
+	}
+
+	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
+	defer delete(storage_key)
+
+	// Start with existing item or create new
+	existing_item: Item
+	if old, has_old := old_item_pre.?; has_old {
+		existing_item = item_deep_copy(old)
+	} else {
+		existing_item = make(Item)
+		for ks in metadata.key_schema {
+			if val, found := key_item[ks.attribute_name]; found {
+				existing_item[strings.clone(ks.attribute_name)] = attr_value_deep_copy(val)
+			}
+		}
+	}
+	defer item_destroy(&existing_item)
+
+	// Apply update plan.
+	if exec_err := execute_update_plan(&existing_item, plan); exec_err != .None {
+		return .Validation_Error
+	}
+
+	// Encode updated item
+	encoded_item, encode_ok := encode(existing_item)
+	if !encode_ok {
+		return .Serialization_Error
+	}
+	defer delete(encoded_item)
+
+	// Add base item to batch
+	rocksdb.batch_put(batch, storage_key, encoded_item)
+
+	// Add old GSI deletions to batch
+	if old, has_old := old_item_pre.?; has_old {
+		gsi_del_err := gsi_batch_delete_entries(batch, table_name, old, metadata)
+		if gsi_del_err != .None {
+			return gsi_del_err
+		}
+	}
+
+	// Add new GSI writes to batch
+	gsi_write_err := gsi_batch_write_entries(batch, table_name, existing_item, metadata)
+	if gsi_write_err != .None {
+		return gsi_write_err
+	}
+
+	return .None
+}
+
+
+// ============================================================================
+// Internal storage operations that skip lock acquisition
+// (Used by transact_write_items which manages its own locking)
+// ============================================================================
+
+get_item_internal :: proc(
+	engine: ^Storage_Engine,
+	table_name: string,
+	key: Item,
+	metadata: ^Table_Metadata,
+) -> (Maybe(Item), Storage_Error) {
+	key_struct, key_ok := key_from_item(key, metadata.key_schema)
+	if !key_ok {
+		return nil, .Missing_Key_Attribute
+	}
+	defer key_destroy(&key_struct)
+
+	key_values, kv_ok := key_get_values(&key_struct)
+	if !kv_ok {
+		return nil, .Invalid_Key
+	}
+
+	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
+	defer delete(storage_key)
+
+	value, get_err := rocksdb.db_get(&engine.db, storage_key)
+	if get_err == .NotFound {
+		return nil, .None
+	}
+	if get_err != .None {
+		return nil, .RocksDB_Error
+	}
+	defer delete(value)
+
+	item, decode_ok := decode(value)
+	if !decode_ok {
+		return nil, .Serialization_Error
+	}
+
+	return item, .None
+}
+
+// ============================================================================
+// TransactGetItems Types
+// ============================================================================
+
+Transact_Get_Action :: struct {
+	table_name: string,
+	key:        Item,
+	projection: Maybe([]string),  // Optional ProjectionExpression paths
+}
+
+Transact_Get_Result :: struct {
+	items: []Maybe(Item),  // One per action, nil if item not found
+}
+
+transact_get_action_destroy :: proc(action: ^Transact_Get_Action) {
+	delete(action.table_name)
+	item_destroy(&action.key)
+	if proj, has := action.projection.?; has {
+		for path in proj {
+			delete(path)
+		}
+		delete(proj)
+	}
+}
+
+transact_get_result_destroy :: proc(result: ^Transact_Get_Result) {
+	for &maybe_item in result.items {
+		if item, has := maybe_item.?; has {
+			item_copy := item
+			item_destroy(&item_copy)
+		}
+	}
+	delete(result.items)
+}
+
+// ============================================================================
+// TransactGetItems — Atomically read up to 100 items
+//
+// DynamoDB semantics:
+//   - All reads are performed with a consistent snapshot
+//   - Missing items are returned as nil (no error)
+//   - ProjectionExpression is applied per-item
+// ============================================================================
+
+transact_get_items :: proc(
+	engine: ^Storage_Engine,
+	actions: []Transact_Get_Action,
+) -> (Transact_Get_Result, Transaction_Error) {
+	result: Transact_Get_Result
+
+	if len(actions) == 0 {
+		return result, .Validation_Error
+	}
+
+	// Collect unique tables and acquire shared locks in deterministic order
+	table_set := make(map[string]bool, allocator = context.temp_allocator)
+	for action in actions {
+		table_set[action.table_name] = true
+	}
+
+	table_names := make([dynamic]string, allocator = context.temp_allocator)
+	for name in table_set {
+		append(&table_names, name)
+	}
+	for i := 0; i < len(table_names); i += 1 {
+		for j := i + 1; j < len(table_names); j += 1 {
+			if table_names[j] < table_names[i] {
+				table_names[i], table_names[j] = table_names[j], table_names[i]
+			}
+		}
+	}
+
+	locks := make([dynamic]^sync.RW_Mutex, allocator = context.temp_allocator)
+	for name in table_names {
+		lock := get_or_create_table_lock(engine, name)
+		sync.rw_mutex_shared_lock(lock)
+		append(&locks, lock)
+	}
+	defer {
+		for i := len(locks) - 1; i >= 0; i -= 1 {
+			sync.rw_mutex_shared_unlock(locks[i])
+		}
+	}
+
+	// Cache metadata
+	metadata_cache := make(map[string]Table_Metadata, allocator = context.temp_allocator)
+	defer {
+		for _, meta in metadata_cache {
+			meta_copy := meta
+			table_metadata_destroy(&meta_copy, engine.allocator)
+		}
+	}
+
+	items := make([]Maybe(Item), len(actions))
+
+	for action, idx in actions {
+		// Get metadata (cached)
+		metadata: ^Table_Metadata
+		if cached, found := &metadata_cache[action.table_name]; found {
+			metadata = cached
+		} else {
+			meta, meta_err := get_table_metadata(engine, action.table_name)
+			if meta_err != .None {
+				items[idx] = nil
+				continue
+			}
+			metadata_cache[action.table_name] = meta
+			metadata = &metadata_cache[action.table_name]
+		}
+
+		// Fetch item
+		item_result, get_err := get_item_internal(engine, action.table_name, action.key, metadata)
+		if get_err != .None {
+			items[idx] = nil
+			continue
+		}
+
+		// Apply projection if specified
+		if item, has_item := item_result.?; has_item {
+			if proj, has_proj := action.projection.?; has_proj && len(proj) > 0 {
+				projected := apply_projection(item, proj)
+				item_copy := item
+				item_destroy(&item_copy)
+				items[idx] = projected
+			} else {
+				items[idx] = item
+			}
+		} else {
+			items[idx] = nil
+		}
+	}
+
+	result.items = items
+	return result, .None
+}
+
+// ============================================================================
+// Helper: Extract modified attribute paths from an Update_Plan
+//
+// Used for UPDATED_NEW / UPDATED_OLD ReturnValues filtering.
+// DynamoDB only returns the attributes that were actually modified
+// by the UpdateExpression, not the entire item.
+// ============================================================================
+
+get_update_plan_modified_paths :: proc(plan: ^Update_Plan) -> []string {
+	paths := make(map[string]bool, allocator = context.temp_allocator)
+
+	for action in plan.sets {
+		paths[action.path] = true
+	}
+	for action in plan.removes {
+		paths[action.path] = true
+	}
+	for action in plan.adds {
+		paths[action.path] = true
+	}
+	for action in plan.deletes {
+		paths[action.path] = true
+	}
+
+	result := make([]string, len(paths))
+	i := 0
+	for path in paths {
+		result[i] = path
+		i += 1
+	}
+	return result
+}
+
+// Filter an item to only include the specified attribute paths.
+// Returns a new deep-copied item containing only matching attributes.
+filter_item_to_paths :: proc(item: Item, paths: []string) -> Item {
+	result := make(Item)
+	for path in paths {
+		if val, found := item[path]; found {
+			result[strings.clone(path)] = attr_value_deep_copy(val)
+		}
+	}
+	return result
+}

dynamodb/types.odin

@@ -5,26 +5,25 @@ import "core:strings"
 
 // DynamoDB AttributeValue - the core data type
 Attribute_Value :: union {
-	String,        // S
+	String,         // S
-	Number,        // N (stored as string)
+	DDB_Number,     // N — decimal-preserving numeric type
-	Binary,        // B (base64)
+	Binary,         // B (base64)
-	Bool,          // BOOL
+	Bool,           // BOOL
-	Null,          // NULL
+	Null,           // NULL
-	String_Set,    // SS
+	String_Set,     // SS
-	Number_Set,    // NS
+	DDB_Number_Set, // NS
-	Binary_Set,    // BS
+	Binary_Set,     // BS
-	List,          // L
+	List,           // L
-	Map,           // M
+	Map,            // M
 }
 
 String :: distinct string
-Number :: distinct string
 Binary :: distinct string
 Bool :: distinct bool
 Null :: distinct bool
 
 String_Set :: distinct []string
-Number_Set :: distinct []string
+DDB_Number_Set :: distinct []DDB_Number
 Binary_Set :: distinct []string
 List :: distinct []Attribute_Value
 Map :: distinct map[string]Attribute_Value
@@ -60,7 +59,7 @@ key_from_item :: proc(item: Item, key_schema: []Key_Schema_Element) -> (Key, boo
 
 		// Validate that key is a scalar type (S, N, or B)
 		#partial switch _ in attr {
-		case String, Number, Binary:
+		case String, DDB_Number, Binary:
 			// Valid key type
 		case:
 			return {}, false
@@ -116,12 +115,11 @@ key_get_values :: proc(key: ^Key) -> (Key_Values, bool) {
 	#partial switch v in key.pk {
 	case String:
 		pk_bytes = transmute([]byte)string(v)
-	case Number:
+	case DDB_Number:
-		pk_bytes = transmute([]byte)string(v)
+		pk_bytes = encode_ddb_number_for_sort(v)
 	case Binary:
 		pk_bytes = transmute([]byte)string(v)
 	case:
-		// Keys should only be scalar types (S, N, or B)
 		return {}, false
 	}
 
@@ -130,12 +128,11 @@ key_get_values :: proc(key: ^Key) -> (Key_Values, bool) {
 		#partial switch v in sk {
 		case String:
 			sk_bytes = transmute([]byte)string(v)
-		case Number:
+		case DDB_Number:
-			sk_bytes = transmute([]byte)string(v)
+			sk_bytes = encode_ddb_number_for_sort(v)
 		case Binary:
 			sk_bytes = transmute([]byte)string(v)
 		case:
-			// Keys should only be scalar types
 			return {}, false
 		}
 	}
@@ -366,13 +363,27 @@ error_to_response :: proc(err_type: DynamoDB_Error_Type, message: string) -> str
 
 // Build an Attribute_Value with the correct scalar type from raw bytes
 build_attribute_value_with_type :: proc(raw_bytes: []byte, attr_type: Scalar_Attribute_Type) -> Attribute_Value {
-	owned := strings.clone(string(raw_bytes))
 	switch attr_type {
-	case .S: return String(owned)
+	case .S:
-	case .N: return Number(owned)
+		return String(strings.clone(string(raw_bytes)))
-	case .B: return Binary(owned)
+	case .N:
+		// Key bytes are canonical-encoded via encode_ddb_number_for_sort.
+		// Decode them back to a DDB_Number.
+		ddb_num, ok := decode_ddb_number_from_sort(raw_bytes)
+		if ok {
+			return clone_ddb_number(ddb_num)
+		}
+		// Fallback: try interpreting as a plain numeric string
+		fallback_num, fb_ok := parse_ddb_number(string(raw_bytes))
+		if fb_ok {
+			return fallback_num
+		}
+		// Last resort — return as string (shouldn't happen)
+		return String(strings.clone(string(raw_bytes)))
+	case .B:
+		return Binary(strings.clone(string(raw_bytes)))
 	}
-	return String(owned)
+	return String(strings.clone(string(raw_bytes)))
 }
 
 // Deep copy an attribute value
@@ -380,8 +391,8 @@ attr_value_deep_copy :: proc(attr: Attribute_Value) -> Attribute_Value {
 	switch v in attr {
 	case String:
 		return String(strings.clone(string(v)))
-	case Number:
+	case DDB_Number:
-		return Number(strings.clone(string(v)))
+		return clone_ddb_number(v)
 	case Binary:
 		return Binary(strings.clone(string(v)))
 	case Bool:
@@ -394,12 +405,12 @@ attr_value_deep_copy :: proc(attr: Attribute_Value) -> Attribute_Value {
 			ss[i] = strings.clone(s)
 		}
 		return String_Set(ss)
-	case Number_Set:
+	case DDB_Number_Set:
-		ns := make([]string, len(v))
+		ddb_ns := make([]DDB_Number, len(v))
-		for n, i in v {
+		for num, i in v {
-			ns[i] = strings.clone(n)
+			ddb_ns[i] = clone_ddb_number(num)
 		}
-		return Number_Set(ns)
+		return DDB_Number_Set(ddb_ns)
 	case Binary_Set:
 		bs := make([]string, len(v))
 		for b, i in v {
@@ -427,8 +438,9 @@ attr_value_destroy :: proc(attr: ^Attribute_Value) {
 	switch v in attr {
 	case String:
 		delete(string(v))
-	case Number:
+	case DDB_Number:
-		delete(string(v))
+		delete(v.integer_part)
+		delete(v.fractional_part)
 	case Binary:
 		delete(string(v))
 	case String_Set:
@@ -437,12 +449,12 @@ attr_value_destroy :: proc(attr: ^Attribute_Value) {
 		}
 		slice := v
 		delete(slice)
-	case Number_Set:
+	case DDB_Number_Set:
-		for n in v {
+		for num in v {
-			delete(n)
+			delete(num.integer_part)
+			delete(num.fractional_part)
 		}
-		slice := v
+		delete(v)
-		delete(slice)
 	case Binary_Set:
 		for b in v {
 			delete(b)

dynamodb/update.odin

@@ -0,0 +1,978 @@
+// UpdateExpression Parser and Executor
+// Supports: SET path = value [, path = value ...]
+//           REMOVE path [, path ...]
+//           ADD path value [, path value ...]    (numeric add / set add)
+//           DELETE path value [, path value ...]  (set remove)
+//
+// Values can be:
+//   :placeholder       → resolved from ExpressionAttributeValues
+//   path + :placeholder → numeric addition
+//   path - :placeholder → numeric subtraction
+//   if_not_exists(path, :placeholder) → default value
+//   list_append(operand, operand)     → list concatenation
+package dynamodb
+
+import "core:encoding/json"
+import "core:strings"
+
+// ============================================================================
+// Update Plan — parsed representation of an UpdateExpression
+// ============================================================================
+
+Update_Action_Type :: enum {
+	SET,
+	REMOVE,
+	ADD,
+	DELETE,
+}
+
+Set_Value_Kind :: enum {
+	Direct,           // SET x = :val
+	Plus,             // SET x = x + :val  or  SET x = :val + x
+	Minus,            // SET x = x - :val
+	If_Not_Exists,    // SET x = if_not_exists(x, :val)
+	List_Append,      // SET x = list_append(x, :val)
+}
+
+Set_Action :: struct {
+	path:       string,
+	value_kind: Set_Value_Kind,
+	value:      Attribute_Value,          // primary value
+	source:     string,                   // source path for Plus/Minus/If_Not_Exists/List_Append
+	value2:     Maybe(Attribute_Value),   // second operand for list_append where both are values
+}
+
+Remove_Action :: struct {
+	path: string,
+}
+
+Add_Action :: struct {
+	path:  string,
+	value: Attribute_Value,
+}
+
+Delete_Action :: struct {
+	path:  string,
+	value: Attribute_Value,
+}
+
+Update_Plan :: struct {
+	sets:    [dynamic]Set_Action,
+	removes: [dynamic]Remove_Action,
+	adds:    [dynamic]Add_Action,
+	deletes: [dynamic]Delete_Action,
+}
+
+update_plan_destroy :: proc(plan: ^Update_Plan) {
+	for &s in plan.sets {
+		attr_value_destroy(&s.value)
+		if v2, ok := s.value2.?; ok {
+			v2_copy := v2
+			attr_value_destroy(&v2_copy)
+		}
+	}
+	delete(plan.sets)
+
+	delete(plan.removes)
+
+	for &a in plan.adds {
+		attr_value_destroy(&a.value)
+	}
+	delete(plan.adds)
+
+	for &d in plan.deletes {
+		attr_value_destroy(&d.value)
+	}
+	delete(plan.deletes)
+}
+
+// ============================================================================
+// Parse UpdateExpression
+//
+// Grammar (simplified):
+//   update_expr = clause { clause }
+//   clause      = "SET" set_list | "REMOVE" remove_list | "ADD" add_list | "DELETE" delete_list
+//   set_list    = set_entry { "," set_entry }
+//   set_entry   = path "=" value_expr
+//   value_expr  = :placeholder
+//              | path "+" :placeholder
+//              | path "-" :placeholder
+//              | "if_not_exists" "(" path "," :placeholder ")"
+//              | "list_append" "(" operand "," operand ")"
+//   remove_list = path { "," path }
+//   add_list    = add_entry { "," add_entry }
+//   add_entry   = path :placeholder
+//   delete_list = delete_entry { "," delete_entry }
+//   delete_entry= path :placeholder
+// ============================================================================
+
+parse_update_expression :: proc(
+	expression: string,
+	attribute_names: Maybe(map[string]string),
+	attribute_values: map[string]Attribute_Value,
+) -> (plan: Update_Plan, ok: bool) {
+	plan.sets    = make([dynamic]Set_Action)
+	plan.removes = make([dynamic]Remove_Action)
+	plan.adds    = make([dynamic]Add_Action)
+	plan.deletes = make([dynamic]Delete_Action)
+
+	t := tokenizer_init(expression)
+
+	for {
+		keyword_maybe := tokenizer_next(&t)
+		keyword_str, has_keyword := keyword_maybe.?
+		if !has_keyword {
+			break // done
+		}
+
+		if strings.equal_fold(keyword_str, "SET") {
+			if !parse_set_clause(&t, &plan, attribute_names, attribute_values) {
+				update_plan_destroy(&plan)
+				return {}, false
+			}
+		} else if strings.equal_fold(keyword_str, "REMOVE") {
+			if !parse_remove_clause(&t, &plan, attribute_names) {
+				update_plan_destroy(&plan)
+				return {}, false
+			}
+		} else if strings.equal_fold(keyword_str, "ADD") {
+			if !parse_add_clause(&t, &plan, attribute_names, attribute_values) {
+				update_plan_destroy(&plan)
+				return {}, false
+			}
+		} else if strings.equal_fold(keyword_str, "DELETE") {
+			if !parse_delete_clause(&t, &plan, attribute_names, attribute_values) {
+				update_plan_destroy(&plan)
+				return {}, false
+			}
+		} else {
+			update_plan_destroy(&plan)
+			return {}, false
+		}
+	}
+
+	return plan, true
+}
+
+// ============================================================================
+// SET clause parsing
+// ============================================================================
+
+parse_set_clause :: proc(
+	t: ^Tokenizer,
+	plan: ^Update_Plan,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> bool {
+	saved_pos: int
+	for {
+		// Save position before reading so we can rewind if it's a clause keyword
+		saved_pos = t.pos
+
+		// Path
+		path_tok, path_ok := next_token(t)
+		if !path_ok {
+			return false
+		}
+
+		// Check if this is actually a new clause keyword (SET/REMOVE/ADD/DELETE)
+		if is_clause_keyword(path_tok) {
+			t.pos = saved_pos
+			return true
+		}
+
+		path, path_resolved := resolve_attribute_name(path_tok, names)
+		if !path_resolved {
+			return false
+		}
+
+		// "="
+		eq_tok, eq_ok := next_token(t)
+		if !eq_ok || eq_tok != "=" {
+			return false
+		}
+
+		// Value expression
+		action, act_ok := parse_set_value_expr(t, path, names, values)
+		if !act_ok {
+			return false
+		}
+
+		append(&plan.sets, action)
+
+		// Check for comma (more entries) or end
+		saved_pos = t.pos
+		comma_maybe := tokenizer_next(t)
+		if comma, has := comma_maybe.?; has {
+			if comma == "," {
+				continue
+			}
+			// Not a comma — put it back
+			t.pos = saved_pos
+		}
+		break
+	}
+	return true
+}
+
+parse_set_value_expr :: proc(
+	t: ^Tokenizer,
+	path: string,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (action: Set_Action, ok: bool) {
+	first_tok, first_ok := next_token(t)
+	if !first_ok {
+		return {}, false
+	}
+
+	// Check for if_not_exists(...)
+	if strings.equal_fold(first_tok, "if_not_exists") {
+		action, ok = parse_if_not_exists(t, path, names, values)
+		return
+	}
+
+	// Check for list_append(...)
+	if strings.equal_fold(first_tok, "list_append") {
+		action, ok = parse_list_append(t, path, names, values)
+		return
+	}
+
+	peek_pos: int
+
+	// Check if first token is a :placeholder (direct value)
+	if len(first_tok) > 0 && first_tok[0] == ':' {
+		// Could be :val + path or :val - path or just :val
+		peek_pos = t.pos
+		op_maybe := tokenizer_next(t)
+		if op, has_op := op_maybe.?; has_op && (op == "+" || op == "-") {
+			// :val op path
+			second_tok, sec_ok := next_token(t)
+			if !sec_ok {
+				return {}, false
+			}
+			source, source_resolved := resolve_attribute_name(second_tok, names)
+			if !source_resolved {
+				return {}, false
+			}
+			val, val_ok := resolve_attribute_value(first_tok, values)
+			if !val_ok {
+				return {}, false
+			}
+			kind := Set_Value_Kind.Plus if op == "+" else Set_Value_Kind.Minus
+			return Set_Action{
+				path       = path,
+				value_kind = kind,
+				value      = val,
+				source     = source,
+			}, true
+		}
+		// Just a direct value
+		t.pos = peek_pos
+		val, val_ok := resolve_attribute_value(first_tok, values)
+		if !val_ok {
+			return {}, false
+		}
+		return Set_Action{
+			path       = path,
+			value_kind = .Direct,
+			value      = val,
+		}, true
+	}
+
+	// First token is a path — check for path + :val or path - :val
+	source, source_resolved := resolve_attribute_name(first_tok, names)
+	if !source_resolved {
+		return {}, false
+	}
+	peek_pos = t.pos
+	op_maybe := tokenizer_next(t)
+	if op, has_op := op_maybe.?; has_op && (op == "+" || op == "-") {
+		val_tok, vt_ok := next_token(t)
+		if !vt_ok {
+			return {}, false
+		}
+		val, val_ok := resolve_attribute_value(val_tok, values)
+		if !val_ok {
+			return {}, false
+		}
+		kind := Set_Value_Kind.Plus if op == "+" else Set_Value_Kind.Minus
+		return Set_Action{
+			path       = path,
+			value_kind = kind,
+			value      = val,
+			source     = source,
+		}, true
+	}
+	// Just a path reference — treat as direct copy (SET a = b)
+	t.pos = peek_pos
+	return {}, false
+}
+
+parse_if_not_exists :: proc(
+	t: ^Tokenizer,
+	path: string,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (action: Set_Action, ok: bool) {
+	lparen, lp_ok := next_token(t)
+	if !lp_ok || lparen != "(" {
+		return {}, false
+	}
+
+	src_tok, src_ok := next_token(t)
+	if !src_ok {
+		return {}, false
+	}
+	source, source_resolved := resolve_attribute_name(src_tok, names)
+	if !source_resolved {
+		return {}, false
+	}
+
+	comma, comma_ok := next_token(t)
+	if !comma_ok || comma != "," {
+		return {}, false
+	}
+
+	val_tok, vt_ok := next_token(t)
+	if !vt_ok {
+		return {}, false
+	}
+	val, val_ok := resolve_attribute_value(val_tok, values)
+	if !val_ok {
+		return {}, false
+	}
+
+	rparen, rp_ok := next_token(t)
+	if !rp_ok || rparen != ")" {
+		attr_value_destroy(&val)
+		return {}, false
+	}
+
+	return Set_Action{
+		path       = path,
+		value_kind = .If_Not_Exists,
+		value      = val,
+		source     = source,
+	}, true
+}
+
+parse_list_append :: proc(
+	t: ^Tokenizer,
+	path: string,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> (action: Set_Action, ok: bool) {
+	lparen, lp_ok := next_token(t)
+	if !lp_ok || lparen != "(" {
+		return {}, false
+	}
+
+	// First operand — could be :val or path
+	first_tok, first_ok := next_token(t)
+	if !first_ok {
+		return {}, false
+	}
+
+	comma, comma_ok := next_token(t)
+	if !comma_ok || comma != "," {
+		return {}, false
+	}
+
+	// Second operand
+	second_tok, second_ok := next_token(t)
+	if !second_ok {
+		return {}, false
+	}
+
+	rparen, rp_ok := next_token(t)
+	if !rp_ok || rparen != ")" {
+		return {}, false
+	}
+
+	// Determine which is the path and which is the value
+	// Common patterns: list_append(path, :val) or list_append(:val, path)
+	source: string
+	val: Attribute_Value
+	resolved: bool
+
+	if len(first_tok) > 0 && first_tok[0] == ':' {
+		// list_append(:val, path)
+		v, v_ok := resolve_attribute_value(first_tok, values)
+		if !v_ok {
+			return {}, false
+		}
+		val = v
+		source, resolved = resolve_attribute_name(second_tok, names)
+		if !resolved {
+			return {}, false
+		}
+	} else if len(second_tok) > 0 && second_tok[0] == ':' {
+		// list_append(path, :val)
+		source, resolved = resolve_attribute_name(first_tok, names)
+		if !resolved {
+			return {}, false
+		}
+		v, v_ok := resolve_attribute_value(second_tok, values)
+		if !v_ok {
+			return {}, false
+		}
+		val = v
+	} else {
+		return {}, false
+	}
+
+	return Set_Action{
+		path       = path,
+		value_kind = .List_Append,
+		value      = val,
+		source     = source,
+	}, true
+}
+
+// ============================================================================
+// REMOVE clause parsing
+// ============================================================================
+
+parse_remove_clause :: proc(
+	t: ^Tokenizer,
+	plan: ^Update_Plan,
+	names: Maybe(map[string]string),
+) -> bool {
+	saved_pos: int
+	for {
+		saved_pos = t.pos
+
+		path_tok, path_ok := next_token(t)
+		if !path_ok {
+			return false
+		}
+
+		if is_clause_keyword(path_tok) {
+			t.pos = saved_pos
+			return true
+		}
+
+		path, path_resolved := resolve_attribute_name(path_tok, names)
+		if !path_resolved {
+			return false
+		}
+
+		append(&plan.removes, Remove_Action{path = path})
+
+		saved_pos = t.pos
+		comma_maybe := tokenizer_next(t)
+		if comma, has := comma_maybe.?; has {
+			if comma == "," {
+				continue
+			}
+			t.pos = saved_pos
+		}
+		break
+	}
+	return true
+}
+
+// ============================================================================
+// ADD clause parsing
+// ============================================================================
+
+parse_add_clause :: proc(
+	t: ^Tokenizer,
+	plan: ^Update_Plan,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> bool {
+	saved_pos: int
+	for {
+		saved_pos = t.pos
+
+		path_tok, path_ok := next_token(t)
+		if !path_ok {
+			return false
+		}
+
+		if is_clause_keyword(path_tok) {
+			t.pos = saved_pos
+			return true
+		}
+
+		path, path_resolved := resolve_attribute_name(path_tok, names)
+		if !path_resolved {
+			return false
+		}
+
+		val_tok, vt_ok := next_token(t)
+		if !vt_ok {
+			return false
+		}
+		val, val_ok := resolve_attribute_value(val_tok, values)
+		if !val_ok {
+			return false
+		}
+
+		append(&plan.adds, Add_Action{path = path, value = val})
+
+		saved_pos = t.pos
+		comma_maybe := tokenizer_next(t)
+		if comma, has := comma_maybe.?; has {
+			if comma == "," {
+				continue
+			}
+			t.pos = saved_pos
+		}
+		break
+	}
+	return true
+}
+
+// ============================================================================
+// DELETE clause parsing
+// ============================================================================
+
+parse_delete_clause :: proc(
+	t: ^Tokenizer,
+	plan: ^Update_Plan,
+	names: Maybe(map[string]string),
+	values: map[string]Attribute_Value,
+) -> bool {
+	saved_pos: int
+	for {
+		saved_pos = t.pos
+
+		path_tok, path_ok := next_token(t)
+		if !path_ok {
+			return false
+		}
+
+		if is_clause_keyword(path_tok) {
+			t.pos = saved_pos
+			return true
+		}
+
+		path, path_resolved := resolve_attribute_name(path_tok, names)
+		if !path_resolved {
+			return false
+		}
+
+		val_tok, vt_ok := next_token(t)
+		if !vt_ok {
+			return false
+		}
+		val, val_ok := resolve_attribute_value(val_tok, values)
+		if !val_ok {
+			return false
+		}
+
+		append(&plan.deletes, Delete_Action{path = path, value = val})
+
+		saved_pos = t.pos
+		comma_maybe := tokenizer_next(t)
+		if comma, has := comma_maybe.?; has {
+			if comma == "," {
+				continue
+			}
+			t.pos = saved_pos
+		}
+		break
+	}
+	return true
+}
+
+// ============================================================================
+// Helpers
+// ============================================================================
+
+is_clause_keyword :: proc(tok: string) -> bool {
+	return strings.equal_fold(tok, "SET") ||
+	       strings.equal_fold(tok, "REMOVE") ||
+	       strings.equal_fold(tok, "ADD") ||
+	       strings.equal_fold(tok, "DELETE")
+}
+
+// ============================================================================
+// Execute Update Plan — apply mutations to an Item (in-place)
+// ============================================================================
+
+// Reasons an update plan can fail at execution time.
+// All of these map to ValidationException at the HTTP layer.
+Update_Exec_Error :: enum {
+	None,
+	// SET x = source +/- val: source attribute does not exist in the item
+	Operand_Not_Found,
+	// SET x = source +/- val: source or value attribute is not a Number
+	Operand_Not_Number,
+	// SET x = list_append(source, val): source attribute is not a List
+	Operand_Not_List,
+	// ADD path val: existing attribute is not a Number, String_Set, or Number_Set
+	Add_Type_Mismatch,
+	// ADD path val: value type does not match the existing set type
+	Add_Value_Type_Mismatch,
+}
+
+execute_update_plan :: proc(item: ^Item, plan: ^Update_Plan) -> Update_Exec_Error {
+	// Execute SET actions
+	for &action in plan.sets {
+		switch action.value_kind {
+		case .Direct:
+			// Remove old value if exists
+			if old, found := item[action.path]; found {
+				old_copy := old
+				attr_value_destroy(&old_copy)
+				delete_key(item, action.path)
+			}
+			item[strings.clone(action.path)] = attr_value_deep_copy(action.value)
+
+		case .Plus:
+			// Numeric addition: path = source + value  or  path = value + source
+			existing: Attribute_Value
+			if src, found := item[action.source]; found {
+				existing = src
+			} else {
+				return .Operand_Not_Found
+			}
+			result, add_ok := numeric_add(existing, action.value)
+			if !add_ok {
+				return .Operand_Not_Number
+			}
+			if old, found := item[action.path]; found {
+				old_copy := old
+				attr_value_destroy(&old_copy)
+				delete_key(item, action.path)
+			}
+			item[strings.clone(action.path)] = result
+
+		case .Minus:
+			// Numeric subtraction: path = source - value
+			existing: Attribute_Value
+			if src, found := item[action.source]; found {
+				existing = src
+			} else {
+				return .Operand_Not_Found
+			}
+			result, sub_ok := numeric_subtract(existing, action.value)
+			if !sub_ok {
+				return .Operand_Not_Number
+			}
+			if old, found := item[action.path]; found {
+				old_copy := old
+				attr_value_destroy(&old_copy)
+				delete_key(item, action.path)
+			}
+			item[strings.clone(action.path)] = result
+
+		case .If_Not_Exists:
+			// Only set if attribute doesn't exist
+			if _, found := item[action.source]; !found {
+				if old, found2 := item[action.path]; found2 {
+					old_copy := old
+					attr_value_destroy(&old_copy)
+					delete_key(item, action.path)
+				}
+				item[strings.clone(action.path)] = attr_value_deep_copy(action.value)
+			}
+			// If attribute exists, do nothing (keep current value)
+
+		case .List_Append:
+			// Append to list
+			existing_list: []Attribute_Value
+			if src, found := item[action.source]; found {
+				if l, is_list := src.(List); is_list {
+					existing_list = ([]Attribute_Value)(l)
+				} else {
+					return .Operand_Not_List
+				}
+			} else {
+				existing_list = {}
+			}
+
+			append_list: []Attribute_Value
+			if l, is_list := action.value.(List); is_list {
+				append_list = ([]Attribute_Value)(l)
+			} else {
+				return .Operand_Not_List
+			}
+
+			new_list := make([]Attribute_Value, len(existing_list) + len(append_list))
+			for item_val, i in existing_list {
+				new_list[i] = attr_value_deep_copy(item_val)
+			}
+			for item_val, i in append_list {
+				new_list[len(existing_list) + i] = attr_value_deep_copy(item_val)
+			}
+
+			if old, found := item[action.path]; found {
+				old_copy := old
+				attr_value_destroy(&old_copy)
+				delete_key(item, action.path)
+			}
+			item[strings.clone(action.path)] = List(new_list)
+		}
+	}
+
+	// Execute REMOVE actions
+	for &action in plan.removes {
+		if old, found := item[action.path]; found {
+			old_copy := old
+			attr_value_destroy(&old_copy)
+			delete_key(item, action.path)
+		}
+	}
+
+	// Execute ADD actions
+	for &action in plan.adds {
+		if existing, found := item[action.path]; found {
+			// If existing is a number, add numerically
+			#partial switch v in existing {
+			case DDB_Number:
+				result, add_ok := numeric_add(existing, action.value)
+				if !add_ok {
+					return .Operand_Not_Number
+				}
+				old_copy := existing
+				attr_value_destroy(&old_copy)
+				delete_key(item, action.path)
+				item[strings.clone(action.path)] = result
+
+			case String_Set:
+				// Add elements to string set
+				if new_ss, is_ss := action.value.(String_Set); is_ss {
+					merged := set_union_strings(([]string)(v), ([]string)(new_ss))
+					old_copy := existing
+					attr_value_destroy(&old_copy)
+					delete_key(item, action.path)
+					item[strings.clone(action.path)] = String_Set(merged)
+				} else {
+					return .Add_Value_Type_Mismatch
+				}
+
+			case DDB_Number_Set:
+				if new_ns, is_ns := action.value.(DDB_Number_Set); is_ns {
+					merged := set_union_ddb_numbers(([]DDB_Number)(v), ([]DDB_Number)(new_ns))
+					old_copy := existing
+					attr_value_destroy(&old_copy)
+					delete_key(item, action.path)
+					item[strings.clone(action.path)] = DDB_Number_Set(merged)
+				} else {
+					return .Add_Value_Type_Mismatch
+				}
+
+			case:
+				return .Add_Type_Mismatch
+			}
+		} else {
+			// Attribute doesn't exist — create it
+			item[strings.clone(action.path)] = attr_value_deep_copy(action.value)
+		}
+	}
+
+	// Execute DELETE actions (remove elements from sets)
+	for &action in plan.deletes {
+		if existing, found := item[action.path]; found {
+			#partial switch v in existing {
+			case String_Set:
+				if del_ss, is_ss := action.value.(String_Set); is_ss {
+					result := set_difference_strings(([]string)(v), ([]string)(del_ss))
+					old_copy := existing
+					attr_value_destroy(&old_copy)
+					delete_key(item, action.path)
+					if len(result) > 0 {
+						item[strings.clone(action.path)] = String_Set(result)
+					} else {
+						delete(result)
+					}
+				}
+
+			case DDB_Number_Set:
+				if del_ns, is_ns := action.value.(DDB_Number_Set); is_ns {
+					result := set_difference_ddb_numbers(([]DDB_Number)(v), ([]DDB_Number)(del_ns))
+					old_copy := existing
+					attr_value_destroy(&old_copy)
+					delete_key(item, action.path)
+					if len(result) > 0 {
+						item[strings.clone(action.path)] = DDB_Number_Set(result)
+					} else {
+						delete(result)
+					}
+				}
+
+			case:
+				// DELETE on non-set type is a no-op in DynamoDB
+			}
+		}
+	}
+
+	return .None
+}
+
+// ============================================================================
+// Numeric helpers
+// ============================================================================
+
+numeric_add :: proc(a: Attribute_Value, b: Attribute_Value) -> (Attribute_Value, bool) {
+	a_num, a_ok := a.(DDB_Number)
+	b_num, b_ok := b.(DDB_Number)
+	if !a_ok || !b_ok {
+		return nil, false
+	}
+
+	result, result_ok := add_ddb_numbers(a_num, b_num)
+	if !result_ok {
+		return nil, false
+	}
+	return result, true
+}
+
+numeric_subtract :: proc(a: Attribute_Value, b: Attribute_Value) -> (Attribute_Value, bool) {
+	a_num, a_ok := a.(DDB_Number)
+	b_num, b_ok := b.(DDB_Number)
+	if !a_ok || !b_ok {
+		return nil, false
+	}
+
+	result, result_ok := subtract_ddb_numbers(a_num, b_num)
+	if !result_ok {
+		return nil, false
+	}
+	return result, true
+}
+
+// ============================================================================
+// Set helpers
+// ============================================================================
+
+set_union_strings :: proc(a: []string, b: []string) -> []string {
+	seen := make(map[string]bool, allocator = context.temp_allocator)
+	for s in a {
+		seen[s] = true
+	}
+	for s in b {
+		seen[s] = true
+	}
+
+	result := make([]string, len(seen))
+	i := 0
+	for s in seen {
+		result[i] = strings.clone(s)
+		i += 1
+	}
+	return result
+}
+
+set_difference_strings :: proc(a: []string, b: []string) -> []string {
+	to_remove := make(map[string]bool, allocator = context.temp_allocator)
+	for s in b {
+		to_remove[s] = true
+	}
+
+	result := make([dynamic]string)
+	for s in a {
+		if !(s in to_remove) {
+			append(&result, strings.clone(s))
+		}
+	}
+	return result[:]
+}
+
+// Union of two DDB_Number slices (dedup by numeric equality)
+set_union_ddb_numbers :: proc(a: []DDB_Number, b: []DDB_Number) -> []DDB_Number {
+	result := make([dynamic]DDB_Number)
+
+	// Add all from a
+	for num in a {
+		append(&result, clone_ddb_number(num))
+	}
+
+	// Add from b if not already present
+	for num in b {
+		found := false
+		for existing in result {
+			if compare_ddb_numbers(existing, num) == 0 {
+				found = true
+				break
+			}
+		}
+		if !found {
+			append(&result, clone_ddb_number(num))
+		}
+	}
+
+	return result[:]
+}
+
+// Difference: elements in a that are NOT in b
+set_difference_ddb_numbers :: proc(a: []DDB_Number, b: []DDB_Number) -> []DDB_Number {
+	result := make([dynamic]DDB_Number)
+
+	for num in a {
+		in_b := false
+		for del in b {
+			if compare_ddb_numbers(num, del) == 0 {
+				in_b = true
+				break
+			}
+		}
+		if !in_b {
+			append(&result, clone_ddb_number(num))
+		}
+	}
+
+	return result[:]
+}
+
+// ============================================================================
+// Request Parsing Helper
+// ============================================================================
+
+parse_update_expression_string :: proc(request_body: []byte) -> (expr: string, ok: bool) {
+	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
+	if parse_err != nil {
+		return
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		return
+	}
+
+	ue_val, found := root["UpdateExpression"]
+	if !found {
+		return
+	}
+
+	ue_str, str_ok := ue_val.(json.String)
+	if !str_ok {
+		return
+	}
+
+	expr = strings.clone(string(ue_str))
+	ok = true
+	return
+}
+
+// Parse ReturnValues from request body
+parse_return_values :: proc(request_body: []byte) -> string {
+	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
+	if parse_err != nil {
+		return strings.clone("NONE")
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		return strings.clone("NONE")
+	}
+
+	rv_val, found := root["ReturnValues"]
+	if !found {
+		return strings.clone("NONE")
+	}
+
+	rv_str, str_ok := rv_val.(json.String)
+	if !str_ok {
+		return strings.clone("NONE")
+	}
+
+	return strings.clone(string(rv_str))
+}

dynamodb/update_item.odin

@@ -0,0 +1,161 @@
+package dynamodb
+
+import "core:strings"
+import "core:sync"
+import "../rocksdb"
+
+// UpdateItem — fetch existing item, apply update plan, write back
+// Uses EXCLUSIVE lock (write operation)
+// ATOMICITY: Uses WriteBatch to ensure base item + all GSI updates are atomic
+//
+// Returns:
+//   - old_item:  the item BEFORE mutations (if it existed), for ReturnValues
+//   - new_item:  the item AFTER mutations
+//   - error
+update_item :: proc(
+	engine: ^Storage_Engine,
+	table_name: string,
+	key_item: Item,
+	plan: ^Update_Plan,
+) -> (old_item: Maybe(Item), new_item: Maybe(Item), err: Storage_Error) {
+	table_lock := get_or_create_table_lock(engine, table_name)
+	sync.rw_mutex_lock(table_lock)
+	defer sync.rw_mutex_unlock(table_lock)
+
+	// Get table metadata
+	metadata, meta_err := get_table_metadata(engine, table_name)
+	if meta_err != .None {
+		return nil, nil, meta_err
+	}
+	defer table_metadata_destroy(&metadata, engine.allocator)
+
+	// Extract key from the provided key item
+	key_struct, key_ok := key_from_item(key_item, metadata.key_schema)
+	if !key_ok {
+		return nil, nil, .Missing_Key_Attribute
+	}
+	defer key_destroy(&key_struct)
+
+	// Get key values
+	key_values, kv_ok := key_get_values(&key_struct)
+	if !kv_ok {
+		return nil, nil, .Invalid_Key
+	}
+
+	// Build storage key
+	storage_key := build_data_key(table_name, key_values.pk, key_values.sk)
+	defer delete(storage_key)
+
+	// Fetch existing item (if any)
+	existing_encoded, get_err := rocksdb.db_get(&engine.db, storage_key)
+	existing_item: Item
+
+	if get_err == .None && existing_encoded != nil {
+		defer delete(existing_encoded)
+
+		decoded, decode_ok := decode(existing_encoded)
+		if !decode_ok {
+			return nil, nil, .Serialization_Error
+		}
+		existing_item = decoded
+		// Save old item for ReturnValues (and for GSI cleanup)
+		old_item = item_deep_copy(existing_item)
+	} else if get_err == .NotFound || existing_encoded == nil {
+		// Item doesn't exist yet — start with just the key attributes
+		existing_item = make(Item)
+
+		for ks in metadata.key_schema {
+			if val, found := key_item[ks.attribute_name]; found {
+				existing_item[strings.clone(ks.attribute_name)] = attr_value_deep_copy(val)
+			}
+		}
+	} else {
+		return nil, nil, .RocksDB_Error
+	}
+
+	// Apply update plan.
+	if exec_err := execute_update_plan(&existing_item, plan); exec_err != .None {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, .Validation_Error
+	}
+
+	// Validate key attributes are still present and correct type
+	validation_err := validate_item_key_types(
+		existing_item, metadata.key_schema, metadata.attribute_definitions,
+	)
+	if validation_err != .None {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, validation_err
+	}
+
+	// Encode updated item
+	encoded_item, encode_ok := encode(existing_item)
+	if !encode_ok {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, .Serialization_Error
+	}
+	defer delete(encoded_item)
+
+	// --- ATOMIC WRITE BATCH: base item + all GSI updates ---
+	batch, batch_err := rocksdb.batch_create()
+	if batch_err != .None {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, .RocksDB_Error
+	}
+	defer rocksdb.batch_destroy(&batch)
+
+	// Add base item write to batch
+	rocksdb.batch_put(&batch, storage_key, encoded_item)
+
+	// Add old GSI entry deletions to batch (if item existed before)
+	if old, has := old_item.?; has {
+		gsi_del_err := gsi_batch_delete_entries(&batch, table_name, old, &metadata)
+		if gsi_del_err != .None {
+			item_destroy(&existing_item)
+			old_copy := old
+			item_destroy(&old_copy)
+			return nil, nil, gsi_del_err
+		}
+	}
+
+	// Add new GSI entry writes to batch
+	gsi_write_err := gsi_batch_write_entries(&batch, table_name, existing_item, &metadata)
+	if gsi_write_err != .None {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, gsi_write_err
+	}
+
+	// Write batch atomically - ALL or NOTHING
+	write_err := rocksdb.batch_write(&engine.db, &batch)
+	if write_err != .None {
+		item_destroy(&existing_item)
+		if old, has := old_item.?; has {
+			old_copy := old
+			item_destroy(&old_copy)
+		}
+		return nil, nil, .RocksDB_Error
+	}
+
+	new_item = existing_item
+	return old_item, new_item, .None
+}

gsi_handlers.odin

@@ -0,0 +1,276 @@
+// gsi_handlers.odin — GSI-related HTTP handler helpers
+//
+// This file lives in the main package alongside main.odin.
+// It provides:
+//   1. parse_global_secondary_indexes — parse GSI definitions from CreateTable request
+//   2. parse_index_name              — extract IndexName from Query/Scan requests
+//   3. Projection type helper for response building
+package main
+
+import "core:encoding/json"
+import "core:strings"
+import "dynamodb"
+
+// ============================================================================
+// Parse GlobalSecondaryIndexes from CreateTable request body
+//
+// DynamoDB CreateTable request format for GSIs:
+// {
+//   "GlobalSecondaryIndexes": [
+//     {
+//       "IndexName": "email-index",
+//       "KeySchema": [
+//         { "AttributeName": "email", "KeyType": "HASH" },
+//         { "AttributeName": "timestamp", "KeyType": "RANGE" }
+//       ],
+//       "Projection": {
+//         "ProjectionType": "ALL" | "KEYS_ONLY" | "INCLUDE",
+//         "NonKeyAttributes": ["attr1", "attr2"]  // only for INCLUDE
+//       }
+//     }
+//   ]
+// }
+//
+// Returns nil if no GSI definitions are present (valid — GSIs are optional).
+// ============================================================================
+
+parse_global_secondary_indexes :: proc(
+	root: json.Object,
+	attr_defs: []dynamodb.Attribute_Definition,
+) -> Maybe([]dynamodb.Global_Secondary_Index) {
+	gsi_val, found := root["GlobalSecondaryIndexes"]
+	if !found {
+		return nil
+	}
+
+	gsi_arr, ok := gsi_val.(json.Array)
+	if !ok || len(gsi_arr) == 0 {
+		return nil
+	}
+
+	gsis := make([]dynamodb.Global_Secondary_Index, len(gsi_arr))
+
+	for elem, i in gsi_arr {
+		elem_obj, elem_ok := elem.(json.Object)
+		if !elem_ok {
+			cleanup_parsed_gsis(gsis[:i])
+			delete(gsis)
+			return nil
+		}
+
+		gsi, gsi_ok := parse_single_gsi(elem_obj, attr_defs)
+		if !gsi_ok {
+			cleanup_parsed_gsis(gsis[:i])
+			delete(gsis)
+			return nil
+		}
+
+		gsis[i] = gsi
+	}
+
+	return gsis
+}
+
+@(private = "file")
+parse_single_gsi :: proc(
+	obj: json.Object,
+	attr_defs: []dynamodb.Attribute_Definition,
+) -> (dynamodb.Global_Secondary_Index, bool) {
+	gsi: dynamodb.Global_Secondary_Index
+
+	// IndexName (required)
+	idx_val, idx_found := obj["IndexName"]
+	if !idx_found {
+		return {}, false
+	}
+	idx_str, idx_ok := idx_val.(json.String)
+	if !idx_ok {
+		return {}, false
+	}
+	gsi.index_name = strings.clone(string(idx_str))
+
+	// KeySchema (required)
+	ks_val, ks_found := obj["KeySchema"]
+	if !ks_found {
+		delete(gsi.index_name)
+		return {}, false
+	}
+	ks_arr, ks_ok := ks_val.(json.Array)
+	if !ks_ok || len(ks_arr) == 0 || len(ks_arr) > 2 {
+		delete(gsi.index_name)
+		return {}, false
+	}
+
+	key_schema := make([]dynamodb.Key_Schema_Element, len(ks_arr))
+	hash_count := 0
+
+	for ks_elem, j in ks_arr {
+		ks_obj, kobj_ok := ks_elem.(json.Object)
+		if !kobj_ok {
+			for k in 0..<j { delete(key_schema[k].attribute_name) }
+			delete(key_schema)
+			delete(gsi.index_name)
+			return {}, false
+		}
+
+		an_val, an_found := ks_obj["AttributeName"]
+		if !an_found {
+			for k in 0..<j { delete(key_schema[k].attribute_name) }
+			delete(key_schema)
+			delete(gsi.index_name)
+			return {}, false
+		}
+		an_str, an_ok := an_val.(json.String)
+		if !an_ok {
+			for k in 0..<j { delete(key_schema[k].attribute_name) }
+			delete(key_schema)
+			delete(gsi.index_name)
+			return {}, false
+		}
+
+		kt_val, kt_found := ks_obj["KeyType"]
+		if !kt_found {
+			for k in 0..<j { delete(key_schema[k].attribute_name) }
+			delete(key_schema)
+			delete(gsi.index_name)
+			return {}, false
+		}
+		kt_str, kt_ok := kt_val.(json.String)
+		if !kt_ok {
+			for k in 0..<j { delete(key_schema[k].attribute_name) }
+			delete(key_schema)
+			delete(gsi.index_name)
+			return {}, false
+		}
+
+		kt, kt_parse_ok := dynamodb.key_type_from_string(string(kt_str))
+		if !kt_parse_ok {
+			for k in 0..<j { delete(key_schema[k].attribute_name) }
+			delete(key_schema)
+			delete(gsi.index_name)
+			return {}, false
+		}
+
+		if kt == .HASH {
+			hash_count += 1
+		}
+
+		// Validate that the GSI key attribute is in AttributeDefinitions
+		attr_defined := false
+		for ad in attr_defs {
+			if ad.attribute_name == string(an_str) {
+				attr_defined = true
+				break
+			}
+		}
+		if !attr_defined {
+			for k in 0..<j { delete(key_schema[k].attribute_name) }
+			delete(key_schema)
+			delete(gsi.index_name)
+			return {}, false
+		}
+
+		key_schema[j] = dynamodb.Key_Schema_Element{
+			attribute_name = strings.clone(string(an_str)),
+			key_type = kt,
+		}
+	}
+
+	// Must have exactly one HASH key
+	if hash_count != 1 {
+		for ks in key_schema { delete(ks.attribute_name) }
+		delete(key_schema)
+		delete(gsi.index_name)
+		return {}, false
+	}
+
+	gsi.key_schema = key_schema
+
+	// Projection (optional — defaults to ALL)
+	gsi.projection.projection_type = .ALL
+	if proj_val, proj_found := obj["Projection"]; proj_found {
+		if proj_obj, proj_ok := proj_val.(json.Object); proj_ok {
+			if pt_val, pt_found := proj_obj["ProjectionType"]; pt_found {
+				if pt_str, pt_ok := pt_val.(json.String); pt_ok {
+					switch string(pt_str) {
+					case "ALL":       gsi.projection.projection_type = .ALL
+					case "KEYS_ONLY": gsi.projection.projection_type = .KEYS_ONLY
+					case "INCLUDE":   gsi.projection.projection_type = .INCLUDE
+					}
+				}
+			}
+
+			// NonKeyAttributes (only valid for INCLUDE projection)
+			if nka_val, nka_found := proj_obj["NonKeyAttributes"]; nka_found {
+				if nka_arr, nka_ok := nka_val.(json.Array); nka_ok && len(nka_arr) > 0 {
+					nka := make([]string, len(nka_arr))
+					for attr_val, k in nka_arr {
+						if attr_str, attr_ok := attr_val.(json.String); attr_ok {
+							nka[k] = strings.clone(string(attr_str))
+						}
+					}
+					gsi.projection.non_key_attributes = nka
+				}
+			}
+		}
+	}
+
+	return gsi, true
+}
+
+@(private = "file")
+cleanup_parsed_gsis :: proc(gsis: []dynamodb.Global_Secondary_Index) {
+	for gsi in gsis {
+		delete(gsi.index_name)
+		for ks in gsi.key_schema {
+			delete(ks.attribute_name)
+		}
+		delete(gsi.key_schema)
+		if nka, has_nka := gsi.projection.non_key_attributes.?; has_nka {
+			for attr in nka { delete(attr) }
+			delete(nka)
+		}
+	}
+}
+
+// ============================================================================
+// Parse IndexName from Query/Scan request
+// ============================================================================
+
+parse_index_name :: proc(request_body: []byte) -> Maybe(string) {
+	data, parse_err := json.parse(request_body, allocator = context.temp_allocator)
+	if parse_err != nil {
+		return nil
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		return nil
+	}
+
+	idx_val, found := root["IndexName"]
+	if !found {
+		return nil
+	}
+
+	idx_str, ok := idx_val.(json.String)
+	if !ok {
+		return nil
+	}
+
+	return strings.clone(string(idx_str))
+}
+
+// ============================================================================
+// Projection type to string for DescribeTable response
+// ============================================================================
+
+projection_type_to_string :: proc(pt: dynamodb.Projection_Type) -> string {
+	switch pt {
+	case .ALL:       return "ALL"
+	case .KEYS_ONLY: return "KEYS_ONLY"
+	case .INCLUDE:   return "INCLUDE"
+	}
+	return "ALL"
+}

http.odin

@@ -6,6 +6,7 @@ import vmem "core:mem/virtual"
 import "core:net"
 import "core:strings"
 import "core:strconv"
+import "core:thread"
 
 // HTTP Method enumeration
 HTTP_Method :: enum {
@@ -100,9 +101,16 @@ response_set_body :: proc(resp: ^HTTP_Response, data: []byte) {
 }
 
 // Request handler function type
-// Takes context pointer, request, and request-scoped allocator
 Request_Handler :: #type proc(ctx: rawptr, request: ^HTTP_Request, request_alloc: mem.Allocator) -> HTTP_Response
 
+// Parse error enum
+Parse_Error :: enum {
+	None,
+	Connection_Closed,
+	Invalid_Request,
+	Body_Too_Large,
+}
+
 // Server configuration
 Server_Config :: struct {
 	max_body_size:              int,  // default 100MB
@@ -122,6 +130,13 @@ default_server_config :: proc() -> Server_Config {
 	}
 }
 
+// Connection task data - passed to worker threads
+Connection_Task_Data :: struct {
+	server: ^Server,
+	conn:   net.TCP_Socket,
+	source: net.Endpoint,
+}
+
 // Server
 Server :: struct {
 	allocator:   mem.Allocator,
@@ -168,9 +183,12 @@ server_start :: proc(server: ^Server) -> bool {
 	server.socket = socket
 	server.running = true
 
-	fmt.printfln("HTTP server listening on %v", server.endpoint)
+	fmt.printfln("HTTP server listening on %v (thread-per-connection)", server.endpoint)
+	fmt.printfln("  Max body size: %d MB", server.config.max_body_size / (1024 * 1024))
+	fmt.printfln("  Max headers: %d", server.config.max_headers)
+	fmt.printfln("  Keep-alive: %v", server.config.enable_keep_alive)
 
-	// Accept loop
+	// Accept loop - spawn a thread for each connection
 	for server.running {
 		conn, source, accept_err := net.accept_tcp(socket)
 		if accept_err != nil {
@@ -180,9 +198,23 @@ server_start :: proc(server: ^Server) -> bool {
 			continue
 		}
 
-		// Handle connection in separate goroutine would go here
+		// Allocate connection data
-		// For now, handle synchronously (should spawn thread)
+		conn_data := new(Connection_Task_Data, server.allocator)
-		handle_connection(server, conn, source)
+		conn_data.server = server
+		conn_data.conn = conn
+		conn_data.source = source
+
+		// Spawn a new thread for this connection
+		t := thread.create(connection_worker_thread)
+		if t != nil {
+			t.init_context = context
+			t.data = conn_data
+			thread.start(t)
+		} else {
+			// Failed to create thread, close connection
+			net.close(conn)
+			free(conn_data, server.allocator)
+		}
 	}
 
 	return true
@@ -190,12 +222,33 @@ server_start :: proc(server: ^Server) -> bool {
 
 server_stop :: proc(server: ^Server) {
 	server.running = false
+
+	// Close listening socket
 	if sock, ok := server.socket.?; ok {
 		net.close(sock)
 		server.socket = nil
 	}
 }
 
+// Worker thread procedure
+connection_worker_thread :: proc(t: ^thread.Thread) {
+	defer thread.destroy(t)
+
+	conn_data := cast(^Connection_Task_Data)t.data
+	defer free(conn_data, conn_data.server.allocator)
+
+	handle_connection(conn_data.server, conn_data.conn, conn_data.source)
+}
+
+// Create error response
+make_error_response_simple :: proc(allocator: mem.Allocator, status: HTTP_Status, message: string) -> HTTP_Response {
+	response := response_init(allocator)
+	response_set_status(&response, status)
+	response_add_header(&response, "Content-Type", "text/plain")
+	response_set_body(&response, transmute([]byte)message)
+	return response
+}
+
 // Handle a single connection
 handle_connection :: proc(server: ^Server, conn: net.TCP_Socket, source: net.Endpoint) {
 	defer net.close(conn)
@@ -214,13 +267,26 @@ handle_connection :: proc(server: ^Server, conn: net.TCP_Socket, source: net.End
 
 		request_alloc := vmem.arena_allocator(&arena)
 
-		// TODO: Double check if we want *all* downstream allocations to use the request arena?
+		// Set request arena as context allocator for downstream allocations
 		old := context.allocator
 		context.allocator = request_alloc
 		defer context.allocator = old
 
-		request, parse_ok := parse_request(conn, request_alloc, server.config)
+		request, parse_err := parse_request(conn, request_alloc, server.config)
-		if !parse_ok {
+
+		// Handle parse errors
+		if parse_err != .None {
+			#partial switch parse_err {
+			case .Body_Too_Large:
+				// Send 413 Payload Too Large
+				response := make_error_response_simple(request_alloc, .Payload_Too_Large,
+					fmt.tprintf("Request body exceeds maximum size of %d bytes", server.config.max_body_size))
+				send_response(conn, &response, request_alloc)
+			case .Invalid_Request:
+				// Send 400 Bad Request
+				response := make_error_response_simple(request_alloc, .Bad_Request, "Invalid HTTP request")
+				send_response(conn, &response, request_alloc)
+			}
 			break
 		}
 
@@ -250,13 +316,13 @@ parse_request :: proc(
 	conn: net.TCP_Socket,
 	allocator: mem.Allocator,
 	config: Server_Config,
-) -> (HTTP_Request, bool) {
+) -> (HTTP_Request, Parse_Error) {
 	// Read request line and headers
 	buffer := make([]byte, config.read_buffer_size, allocator)
 
 	bytes_read, read_err := net.recv_tcp(conn, buffer)
 	if read_err != nil || bytes_read == 0 {
-		return {}, false
+		return {}, .Connection_Closed
 	}
 
 	request_data := buffer[:bytes_read]
@@ -264,7 +330,7 @@ parse_request :: proc(
 	// Find end of headers (\r\n\r\n)
 	header_end_idx := strings.index(string(request_data), "\r\n\r\n")
 	if header_end_idx < 0 {
-		return {}, false
+		return {}, .Invalid_Request
 	}
 
 	header_section := string(request_data[:header_end_idx])
@@ -273,13 +339,13 @@ parse_request :: proc(
 	// Parse request line
 	lines := strings.split_lines(header_section, allocator)
 	if len(lines) == 0 {
-		return {}, false
+		return {}, .Invalid_Request
 	}
 
 	request_line := lines[0]
 	parts := strings.split(request_line, " ", allocator)
 	if len(parts) < 3 {
-		return {}, false
+		return {}, .Invalid_Request
 	}
 
 	method := method_from_string(parts[0])
@@ -305,6 +371,11 @@ parse_request :: proc(
 			name  = strings.clone(name, allocator),
 			value = strings.clone(value, allocator),
 		})
+
+		// Check max headers limit
+		if len(headers) > config.max_headers {
+			return {}, .Invalid_Request
+		}
 	}
 
 	// Read body if Content-Length present
@@ -314,7 +385,12 @@ parse_request :: proc(
 	if cl, ok := content_length_header.?; ok {
 		content_length := strconv.parse_int(cl) or_else 0
 
-		if content_length > 0 && content_length <= config.max_body_size {
+		// Check if body size exceeds limit
+		if content_length > config.max_body_size {
+			return {}, .Body_Too_Large
+		}
+
+		if content_length > 0 {
 			// Check if we already have the body in buffer
 			existing_body := request_data[body_start:]
 
@@ -336,7 +412,7 @@ parse_request :: proc(
 
 					n, err := net.recv_tcp(conn, chunk)
 					if err != nil || n == 0 {
-						return {}, false
+						return {}, .Connection_Closed
 					}
 
 					copy(body[body_written:], chunk[:n])
@@ -352,7 +428,7 @@ parse_request :: proc(
 		path    = path,
 		headers = headers[:],
 		body    = body,
-	}, true
+	}, .None
 }
 
 // Helper to get header from slice

open_api_doc.yaml

@@ -0,0 +1,884 @@
+openapi: 3.0.3
+info:
+  title: JormunDB DynamoDB Wire API
+  version: 0.1.0
+  description: |
+    DynamoDB-compatible JSON-over-HTTP API implemented by JormunDB.
+    Requests are POSTed to a single endpoint (/) and routed by the required `X-Amz-Target` header.
+servers:
+  - url: http://localhost:8002
+
+paths:
+  /:
+    post:
+      summary: DynamoDB JSON API endpoint
+      description: |
+        Send DynamoDB JSON protocol requests to this endpoint and set `X-Amz-Target` to the operation name,
+        e.g. `DynamoDB_20120810.GetItem`. The request and response media type is typically
+        `application/x-amz-json-1.0`.
+      parameters:
+        - $ref: '#/components/parameters/XAmzTarget'
+        - $ref: '#/components/parameters/XAmzDate'
+        - $ref: '#/components/parameters/Authorization'
+        - $ref: '#/components/parameters/XAmzSecurityToken'
+        - $ref: '#/components/parameters/XAmzContentSha256'
+      requestBody:
+        required: true
+        content:
+          application/x-amz-json-1.0:
+            schema:
+              oneOf:
+                - $ref: '#/components/schemas/CreateTableRequest'
+                - $ref: '#/components/schemas/DeleteTableRequest'
+                - $ref: '#/components/schemas/DescribeTableRequest'
+                - $ref: '#/components/schemas/ListTablesRequest'
+                - $ref: '#/components/schemas/PutItemRequest'
+                - $ref: '#/components/schemas/GetItemRequest'
+                - $ref: '#/components/schemas/DeleteItemRequest'
+                - $ref: '#/components/schemas/UpdateItemRequest'
+                - $ref: '#/components/schemas/QueryRequest'
+                - $ref: '#/components/schemas/ScanRequest'
+                - $ref: '#/components/schemas/BatchWriteItemRequest'
+                - $ref: '#/components/schemas/BatchGetItemRequest'
+                - $ref: '#/components/schemas/TransactWriteItemsRequest'
+                - $ref: '#/components/schemas/TransactGetItemsRequest'
+            examples:
+              CreateTable:
+                summary: Create a table with a HASH key
+                value:
+                  TableName: ExampleTable
+                  KeySchema:
+                    - AttributeName: pk
+                      KeyType: HASH
+                  AttributeDefinitions:
+                    - AttributeName: pk
+                      AttributeType: S
+      responses:
+        '200':
+          description: Successful operation response
+          content:
+            application/x-amz-json-1.0:
+              schema:
+                oneOf:
+                  - $ref: '#/components/schemas/CreateTableResponse'
+                  - $ref: '#/components/schemas/DeleteTableResponse'
+                  - $ref: '#/components/schemas/DescribeTableResponse'
+                  - $ref: '#/components/schemas/ListTablesResponse'
+                  - $ref: '#/components/schemas/PutItemResponse'
+                  - $ref: '#/components/schemas/GetItemResponseUnion'
+                  - $ref: '#/components/schemas/DeleteItemResponse'
+                  - $ref: '#/components/schemas/UpdateItemResponseUnion'
+                  - $ref: '#/components/schemas/QueryResponse'
+                  - $ref: '#/components/schemas/ScanResponse'
+                  - $ref: '#/components/schemas/BatchWriteItemResponse'
+                  - $ref: '#/components/schemas/BatchGetItemResponse'
+                  - $ref: '#/components/schemas/TransactWriteItemsResponse'
+                  - $ref: '#/components/schemas/TransactGetItemsResponse'
+        '400':
+          description: Client error (ValidationException, SerializationException, etc.)
+          content:
+            application/x-amz-json-1.0:
+              schema:
+                oneOf:
+                  - $ref: '#/components/schemas/DynamoDbError'
+                  - $ref: '#/components/schemas/TransactionCanceledException'
+        '500':
+          description: Server error
+          content:
+            application/x-amz-json-1.0:
+              schema:
+                $ref: '#/components/schemas/DynamoDbError'
+
+components:
+  parameters:
+    XAmzTarget:
+      name: X-Amz-Target
+      in: header
+      required: true
+      description: |
+        DynamoDB JSON protocol operation selector.
+        JormunDB recognizes targets with the `DynamoDB_20120810.` prefix.
+        Note: `UpdateTable` may be recognized but not implemented.
+      schema:
+        type: string
+        enum:
+          - DynamoDB_20120810.CreateTable
+          - DynamoDB_20120810.DeleteTable
+          - DynamoDB_20120810.DescribeTable
+          - DynamoDB_20120810.ListTables
+          - DynamoDB_20120810.UpdateTable
+          - DynamoDB_20120810.PutItem
+          - DynamoDB_20120810.GetItem
+          - DynamoDB_20120810.DeleteItem
+          - DynamoDB_20120810.UpdateItem
+          - DynamoDB_20120810.Query
+          - DynamoDB_20120810.Scan
+          - DynamoDB_20120810.BatchGetItem
+          - DynamoDB_20120810.BatchWriteItem
+          - DynamoDB_20120810.TransactGetItems
+          - DynamoDB_20120810.TransactWriteItems
+      example: DynamoDB_20120810.GetItem
+
+    XAmzDate:
+      name: X-Amz-Date
+      in: header
+      required: false
+      schema:
+        type: string
+      description: Optional SigV4 timestamp header (kept for SDK compatibility).
+
+    Authorization:
+      name: Authorization
+      in: header
+      required: false
+      schema:
+        type: string
+      description: Optional SigV4 Authorization header (kept for SDK compatibility).
+
+    XAmzSecurityToken:
+      name: X-Amz-Security-Token
+      in: header
+      required: false
+      schema:
+        type: string
+      description: Optional SigV4 session token header (kept for SDK compatibility).
+
+    XAmzContentSha256:
+      name: X-Amz-Content-Sha256
+      in: header
+      required: false
+      schema:
+        type: string
+      description: Optional SigV4 payload hash header (kept for SDK compatibility).
+
+  schemas:
+    EmptyObject:
+      type: object
+      description: Empty JSON object.
+      additionalProperties: false
+
+    # -------------------------
+    # AttributeValue & helpers
+    # -------------------------
+    AttributeValue:
+      description: DynamoDB AttributeValue (JSON wire format).
+      type: object
+      minProperties: 1
+      maxProperties: 1
+      oneOf:
+        - $ref: '#/components/schemas/AttrS'
+        - $ref: '#/components/schemas/AttrN'
+        - $ref: '#/components/schemas/AttrB'
+        - $ref: '#/components/schemas/AttrBOOL'
+        - $ref: '#/components/schemas/AttrNULL'
+        - $ref: '#/components/schemas/AttrSS'
+        - $ref: '#/components/schemas/AttrNS'
+        - $ref: '#/components/schemas/AttrBS'
+        - $ref: '#/components/schemas/AttrL'
+        - $ref: '#/components/schemas/AttrM'
+
+    AttrS:
+      type: object
+      additionalProperties: false
+      required: [S]
+      properties:
+        S:
+          type: string
+          example: hello
+
+    AttrN:
+      type: object
+      additionalProperties: false
+      required: [N]
+      properties:
+        N:
+          type: string
+          description: Numeric values are encoded as strings in DynamoDB's JSON protocol.
+          example: "42"
+
+    AttrB:
+      type: object
+      additionalProperties: false
+      required: [B]
+      properties:
+        B:
+          type: string
+          description: Base64-encoded binary value.
+          example: AAECAwQ=
+
+    AttrBOOL:
+      type: object
+      additionalProperties: false
+      required: [BOOL]
+      properties:
+        BOOL:
+          type: boolean
+          example: true
+
+    AttrNULL:
+      type: object
+      additionalProperties: false
+      required: [NULL]
+      properties:
+        NULL:
+          type: boolean
+          enum: [true]
+          example: true
+
+    AttrSS:
+      type: object
+      additionalProperties: false
+      required: [SS]
+      properties:
+        SS:
+          type: array
+          items: { type: string }
+          example: [a, b]
+
+    AttrNS:
+      type: object
+      additionalProperties: false
+      required: [NS]
+      properties:
+        NS:
+          type: array
+          description: Numeric set values are encoded as strings.
+          items: { type: string }
+          example: ["1", "2"]
+
+    AttrBS:
+      type: object
+      additionalProperties: false
+      required: [BS]
+      properties:
+        BS:
+          type: array
+          description: Base64-encoded binary set values.
+          items: { type: string }
+          example: [AAE=, AgM=]
+
+    AttrL:
+      type: object
+      additionalProperties: false
+      required: [L]
+      properties:
+        L:
+          type: array
+          items:
+            $ref: '#/components/schemas/AttributeValue'
+
+    AttrM:
+      type: object
+      additionalProperties: false
+      required: [M]
+      properties:
+        M:
+          $ref: '#/components/schemas/AttributeMap'
+
+    AttributeMap:
+      type: object
+      additionalProperties:
+        $ref: '#/components/schemas/AttributeValue'
+      example:
+        pk: { S: "user#1" }
+        sk: { S: "meta" }
+        age: { N: "30" }
+
+    ExpressionAttributeNames:
+      type: object
+      additionalProperties: { type: string }
+      example:
+        "#pk": "pk"
+
+    ExpressionAttributeValues:
+      type: object
+      additionalProperties:
+        $ref: '#/components/schemas/AttributeValue'
+      example:
+        ":v": { S: "user#1" }
+
+    Key:
+      allOf:
+        - $ref: '#/components/schemas/AttributeMap'
+      description: Primary key map (HASH, optionally RANGE) encoded as an AttributeMap.
+
+    ReturnValues:
+      type: string
+      description: ReturnValues selector used by UpdateItem.
+      enum: [NONE, ALL_OLD, UPDATED_OLD, ALL_NEW, UPDATED_NEW]
+      example: ALL_NEW
+
+    # -------------------------
+    # Table shapes
+    # -------------------------
+    ScalarAttributeType:
+      type: string
+      enum: [S, N, B]
+      example: S
+
+    AttributeDefinition:
+      type: object
+      additionalProperties: false
+      required: [AttributeName, AttributeType]
+      properties:
+        AttributeName: { type: string }
+        AttributeType: { $ref: '#/components/schemas/ScalarAttributeType' }
+
+    KeyType:
+      type: string
+      enum: [HASH, RANGE]
+      example: HASH
+
+    KeySchemaElement:
+      type: object
+      additionalProperties: false
+      required: [AttributeName, KeyType]
+      properties:
+        AttributeName: { type: string }
+        KeyType: { $ref: '#/components/schemas/KeyType' }
+
+    ProjectionType:
+      type: string
+      enum: [KEYS_ONLY, INCLUDE, ALL]
+      example: ALL
+
+    Projection:
+      type: object
+      additionalProperties: false
+      required: [ProjectionType]
+      properties:
+        ProjectionType: { $ref: '#/components/schemas/ProjectionType' }
+        NonKeyAttributes:
+          type: array
+          items: { type: string }
+
+    GlobalSecondaryIndex:
+      type: object
+      additionalProperties: false
+      required: [IndexName, KeySchema, Projection]
+      properties:
+        IndexName: { type: string }
+        KeySchema:
+          type: array
+          items: { $ref: '#/components/schemas/KeySchemaElement' }
+          minItems: 1
+        Projection: { $ref: '#/components/schemas/Projection' }
+
+    TableStatus:
+      type: string
+      enum: [CREATING, UPDATING, DELETING, ACTIVE, ARCHIVING, ARCHIVED]
+      example: ACTIVE
+
+    TableDescription:
+      type: object
+      additionalProperties: false
+      required: [TableName, TableStatus]
+      properties:
+        TableName: { type: string }
+        TableStatus: { $ref: '#/components/schemas/TableStatus' }
+        CreationDateTime:
+          type: integer
+          format: int64
+          description: Unix epoch seconds.
+        KeySchema:
+          type: array
+          items: { $ref: '#/components/schemas/KeySchemaElement' }
+        AttributeDefinitions:
+          type: array
+          items: { $ref: '#/components/schemas/AttributeDefinition' }
+        GlobalSecondaryIndexes:
+          type: array
+          items:
+            allOf:
+              - $ref: '#/components/schemas/GlobalSecondaryIndex'
+              - type: object
+                properties:
+                  IndexStatus:
+                    type: string
+                    enum: [ACTIVE]
+
+    # -------------------------
+    # Error shapes
+    # -------------------------
+    DynamoDbError:
+      type: object
+      additionalProperties: false
+      required: [__type, message]
+      properties:
+        __type:
+          type: string
+          description: DynamoDB error type identifier.
+          example: com.amazonaws.dynamodb.v20120810#ValidationException
+        message:
+          type: string
+          example: Invalid request
+
+    TransactionCanceledException:
+      type: object
+      additionalProperties: false
+      required: [__type, message, CancellationReasons]
+      properties:
+        __type:
+          type: string
+          enum: [com.amazonaws.dynamodb.v20120810#TransactionCanceledException]
+        message:
+          type: string
+        CancellationReasons:
+          type: array
+          items:
+            type: object
+            additionalProperties: false
+            required: [Code, Message]
+            properties:
+              Code: { type: string, example: ConditionalCheckFailed }
+              Message: { type: string, example: The conditional request failed }
+
+    # -------------------------
+    # API: CreateTable
+    # -------------------------
+    CreateTableRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName, KeySchema, AttributeDefinitions]
+      properties:
+        TableName: { type: string }
+        KeySchema:
+          type: array
+          items: { $ref: '#/components/schemas/KeySchemaElement' }
+          minItems: 1
+        AttributeDefinitions:
+          type: array
+          items: { $ref: '#/components/schemas/AttributeDefinition' }
+          minItems: 1
+        GlobalSecondaryIndexes:
+          type: array
+          items: { $ref: '#/components/schemas/GlobalSecondaryIndex' }
+      description: |
+        CreateTable request. JormunDB focuses on TableName, KeySchema, AttributeDefinitions, and optional GSI definitions.
+
+    CreateTableResponse:
+      type: object
+      additionalProperties: false
+      required: [TableDescription]
+      properties:
+        TableDescription:
+          type: object
+          additionalProperties: false
+          required: [TableName, TableStatus, CreationDateTime]
+          properties:
+            TableName: { type: string }
+            TableStatus: { $ref: '#/components/schemas/TableStatus' }
+            CreationDateTime: { type: integer, format: int64 }
+
+    # -------------------------
+    # API: DeleteTable / DescribeTable / ListTables
+    # -------------------------
+    DeleteTableRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName]
+      properties:
+        TableName: { type: string }
+
+    DeleteTableResponse:
+      type: object
+      additionalProperties: false
+      required: [TableDescription]
+      properties:
+        TableDescription:
+          type: object
+          additionalProperties: false
+          required: [TableName, TableStatus]
+          properties:
+            TableName: { type: string }
+            TableStatus:
+              type: string
+              enum: [DELETING]
+
+    DescribeTableRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName]
+      properties:
+        TableName: { type: string }
+
+    DescribeTableResponse:
+      type: object
+      additionalProperties: false
+      required: [Table]
+      properties:
+        Table: { $ref: '#/components/schemas/TableDescription' }
+
+    ListTablesRequest:
+      type: object
+      additionalProperties: true
+      description: ListTables request. JormunDB ignores request fields for this operation.
+
+    ListTablesResponse:
+      type: object
+      additionalProperties: false
+      required: [TableNames]
+      properties:
+        TableNames:
+          type: array
+          items: { type: string }
+
+    # -------------------------
+    # API: PutItem / GetItem / DeleteItem
+    # -------------------------
+    PutItemRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName, Item]
+      properties:
+        TableName: { type: string }
+        Item: { $ref: '#/components/schemas/AttributeMap' }
+        ConditionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+
+    PutItemResponse:
+      $ref: '#/components/schemas/EmptyObject'
+
+    GetItemRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName, Key]
+      properties:
+        TableName: { type: string }
+        Key: { $ref: '#/components/schemas/Key' }
+        ProjectionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+
+    GetItemResponse:
+      type: object
+      additionalProperties: false
+      required: [Item]
+      properties:
+        Item: { $ref: '#/components/schemas/AttributeMap' }
+
+    GetItemResponseUnion:
+      oneOf:
+        - $ref: '#/components/schemas/EmptyObject'
+        - $ref: '#/components/schemas/GetItemResponse'
+
+    DeleteItemRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName, Key]
+      properties:
+        TableName: { type: string }
+        Key: { $ref: '#/components/schemas/Key' }
+        ConditionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+
+    DeleteItemResponse:
+      $ref: '#/components/schemas/EmptyObject'
+
+    # -------------------------
+    # API: UpdateItem
+    # -------------------------
+    UpdateItemRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName, Key, UpdateExpression]
+      properties:
+        TableName: { type: string }
+        Key: { $ref: '#/components/schemas/Key' }
+        UpdateExpression: { type: string }
+        ConditionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+        ReturnValues: { $ref: '#/components/schemas/ReturnValues' }
+
+    UpdateItemResponse:
+      type: object
+      additionalProperties: false
+      required: [Attributes]
+      properties:
+        Attributes: { $ref: '#/components/schemas/AttributeMap' }
+
+    UpdateItemResponseUnion:
+      oneOf:
+        - $ref: '#/components/schemas/EmptyObject'
+        - $ref: '#/components/schemas/UpdateItemResponse'
+
+    # -------------------------
+    # API: Query / Scan
+    # -------------------------
+    QueryRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName, KeyConditionExpression]
+      properties:
+        TableName: { type: string }
+        IndexName: { type: string }
+        KeyConditionExpression: { type: string }
+        FilterExpression: { type: string }
+        ProjectionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+        Limit:
+          type: integer
+          format: int32
+          minimum: 1
+          description: Maximum items to return (default 100 if omitted/0 in JormunDB).
+        ExclusiveStartKey: { $ref: '#/components/schemas/Key' }
+        ScanIndexForward:
+          type: boolean
+          description: Sort order for RANGE key queries (if applicable).
+
+    ScanRequest:
+      type: object
+      additionalProperties: true
+      required: [TableName]
+      properties:
+        TableName: { type: string }
+        IndexName: { type: string }
+        FilterExpression: { type: string }
+        ProjectionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+        Limit:
+          type: integer
+          format: int32
+          minimum: 1
+          description: Maximum items to return (default 100 if omitted/0 in JormunDB).
+        ExclusiveStartKey: { $ref: '#/components/schemas/Key' }
+
+    ItemsPage:
+      type: object
+      additionalProperties: false
+      required: [Items, Count, ScannedCount]
+      properties:
+        Items:
+          type: array
+          items: { $ref: '#/components/schemas/AttributeMap' }
+        Count:
+          type: integer
+          format: int32
+        ScannedCount:
+          type: integer
+          format: int32
+        LastEvaluatedKey:
+          $ref: '#/components/schemas/Key'
+
+    QueryResponse:
+      allOf:
+        - $ref: '#/components/schemas/ItemsPage'
+
+    ScanResponse:
+      allOf:
+        - $ref: '#/components/schemas/ItemsPage'
+
+    # -------------------------
+    # API: BatchWriteItem
+    # -------------------------
+    WriteRequest:
+      type: object
+      additionalProperties: false
+      properties:
+        PutRequest:
+          type: object
+          additionalProperties: false
+          required: [Item]
+          properties:
+            Item: { $ref: '#/components/schemas/AttributeMap' }
+        DeleteRequest:
+          type: object
+          additionalProperties: false
+          required: [Key]
+          properties:
+            Key: { $ref: '#/components/schemas/Key' }
+      oneOf:
+        - required: [PutRequest]
+        - required: [DeleteRequest]
+
+    BatchWriteItemRequest:
+      type: object
+      additionalProperties: true
+      required: [RequestItems]
+      properties:
+        RequestItems:
+          type: object
+          description: Map of table name to write requests.
+          additionalProperties:
+            type: array
+            items: { $ref: '#/components/schemas/WriteRequest' }
+
+    BatchWriteItemResponse:
+      type: object
+      additionalProperties: false
+      required: [UnprocessedItems]
+      properties:
+        UnprocessedItems:
+          type: object
+          additionalProperties:
+            type: array
+            items: { $ref: '#/components/schemas/WriteRequest' }
+
+    # -------------------------
+    # API: BatchGetItem
+    # -------------------------
+    KeysAndAttributes:
+      type: object
+      additionalProperties: true
+      required: [Keys]
+      properties:
+        Keys:
+          type: array
+          items: { $ref: '#/components/schemas/Key' }
+        ProjectionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+
+    BatchGetItemRequest:
+      type: object
+      additionalProperties: true
+      required: [RequestItems]
+      properties:
+        RequestItems:
+          type: object
+          additionalProperties:
+            $ref: '#/components/schemas/KeysAndAttributes'
+
+    BatchGetItemResponse:
+      type: object
+      additionalProperties: false
+      required: [Responses, UnprocessedKeys]
+      properties:
+        Responses:
+          type: object
+          additionalProperties:
+            type: array
+            items: { $ref: '#/components/schemas/AttributeMap' }
+        UnprocessedKeys:
+          type: object
+          additionalProperties:
+            $ref: '#/components/schemas/KeysAndAttributes'
+
+    # -------------------------
+    # API: TransactWriteItems / TransactGetItems
+    # -------------------------
+    TransactWriteItemsRequest:
+      type: object
+      additionalProperties: true
+      required: [TransactItems]
+      properties:
+        TransactItems:
+          type: array
+          minItems: 1
+          maxItems: 100
+          items:
+            $ref: '#/components/schemas/TransactWriteItem'
+
+    TransactWriteItem:
+      type: object
+      additionalProperties: false
+      oneOf:
+        - required: [Put]
+        - required: [Delete]
+        - required: [Update]
+        - required: [ConditionCheck]
+      properties:
+        Put:
+          $ref: '#/components/schemas/TransactPut'
+        Delete:
+          $ref: '#/components/schemas/TransactDelete'
+        Update:
+          $ref: '#/components/schemas/TransactUpdate'
+        ConditionCheck:
+          $ref: '#/components/schemas/TransactConditionCheck'
+
+    TransactPut:
+      type: object
+      additionalProperties: true
+      required: [TableName, Item]
+      properties:
+        TableName: { type: string }
+        Item: { $ref: '#/components/schemas/AttributeMap' }
+        ConditionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+
+    TransactDelete:
+      type: object
+      additionalProperties: true
+      required: [TableName, Key]
+      properties:
+        TableName: { type: string }
+        Key: { $ref: '#/components/schemas/Key' }
+        ConditionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+
+    TransactUpdate:
+      type: object
+      additionalProperties: true
+      required: [TableName, Key, UpdateExpression]
+      properties:
+        TableName: { type: string }
+        Key: { $ref: '#/components/schemas/Key' }
+        UpdateExpression: { type: string }
+        ConditionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+
+    TransactConditionCheck:
+      type: object
+      additionalProperties: true
+      required: [TableName, Key, ConditionExpression]
+      properties:
+        TableName: { type: string }
+        Key: { $ref: '#/components/schemas/Key' }
+        ConditionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+        ExpressionAttributeValues: { $ref: '#/components/schemas/ExpressionAttributeValues' }
+
+    TransactWriteItemsResponse:
+      $ref: '#/components/schemas/EmptyObject'
+
+    TransactGetItemsRequest:
+      type: object
+      additionalProperties: true
+      required: [TransactItems]
+      properties:
+        TransactItems:
+          type: array
+          minItems: 1
+          maxItems: 100
+          items:
+            type: object
+            additionalProperties: false
+            required: [Get]
+            properties:
+              Get:
+                $ref: '#/components/schemas/TransactGet'
+
+    TransactGet:
+      type: object
+      additionalProperties: true
+      required: [TableName, Key]
+      properties:
+        TableName: { type: string }
+        Key: { $ref: '#/components/schemas/Key' }
+        ProjectionExpression: { type: string }
+        ExpressionAttributeNames: { $ref: '#/components/schemas/ExpressionAttributeNames' }
+
+    TransactGetItemResult:
+      oneOf:
+        - $ref: '#/components/schemas/EmptyObject'
+        - type: object
+          additionalProperties: false
+          required: [Item]
+          properties:
+            Item: { $ref: '#/components/schemas/AttributeMap' }
+
+    TransactGetItemsResponse:
+      type: object
+      additionalProperties: false
+      required: [Responses]
+      properties:
+        Responses:
+          type: array
+          items: { $ref: '#/components/schemas/TransactGetItemResult' }

transact_handlers.odin

@@ -0,0 +1,599 @@
+// transact_handlers.odin — HTTP handlers for TransactWriteItems and TransactGetItems
+//
+// Also contains the UPDATED_NEW / UPDATED_OLD filtering helper for UpdateItem.
+package main
+
+import "core:encoding/json"
+import "core:fmt"
+import "core:strings"
+import "dynamodb"
+
+// ============================================================================
+// TransactWriteItems Handler
+//
+// Request format:
+// {
+//   "TransactItems": [
+//     {
+//       "Put": {
+//         "TableName": "...",
+//         "Item": { ... },
+//         "ConditionExpression": "...",          // optional
+//         "ExpressionAttributeNames": { ... },   // optional
+//         "ExpressionAttributeValues": { ... }    // optional
+//       }
+//     },
+//     {
+//       "Delete": {
+//         "TableName": "...",
+//         "Key": { ... },
+//         "ConditionExpression": "...",           // optional
+//         ...
+//       }
+//     },
+//     {
+//       "Update": {
+//         "TableName": "...",
+//         "Key": { ... },
+//         "UpdateExpression": "...",
+//         "ConditionExpression": "...",           // optional
+//         "ExpressionAttributeNames": { ... },   // optional
+//         "ExpressionAttributeValues": { ... }    // optional
+//       }
+//     },
+//     {
+//       "ConditionCheck": {
+//         "TableName": "...",
+//         "Key": { ... },
+//         "ConditionExpression": "...",
+//         "ExpressionAttributeNames": { ... },   // optional
+//         "ExpressionAttributeValues": { ... }    // optional
+//       }
+//     }
+//   ]
+// }
+// ============================================================================
+
+handle_transact_write_items :: proc(
+	engine: ^dynamodb.Storage_Engine,
+	request: ^HTTP_Request,
+	response: ^HTTP_Response,
+) {
+	data, parse_err := json.parse(request.body, allocator = context.allocator)
+	if parse_err != nil {
+		make_error_response(response, .SerializationException, "Invalid JSON")
+		return
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		make_error_response(response, .SerializationException, "Request must be an object")
+		return
+	}
+
+	transact_items_val, found := root["TransactItems"]
+	if !found {
+		make_error_response(response, .ValidationException, "Missing TransactItems")
+		return
+	}
+
+	transact_items, ti_ok := transact_items_val.(json.Array)
+	if !ti_ok {
+		make_error_response(response, .ValidationException, "TransactItems must be an array")
+		return
+	}
+
+	if len(transact_items) == 0 {
+		make_error_response(response, .ValidationException,
+			"TransactItems must contain at least one item")
+		return
+	}
+
+	if len(transact_items) > 100 {
+		make_error_response(response, .ValidationException,
+			"Member must have length less than or equal to 100")
+		return
+	}
+
+	// Parse each action
+	actions := make([dynamic]dynamodb.Transact_Write_Action)
+	defer {
+		for &action in actions {
+			dynamodb.transact_write_action_destroy(&action)
+		}
+		delete(actions)
+	}
+
+	for elem in transact_items {
+		elem_obj, elem_ok := elem.(json.Object)
+		if !elem_ok {
+			make_error_response(response, .ValidationException,
+				"Each TransactItem must be an object")
+			return
+		}
+
+		action, action_ok := parse_transact_write_action(elem_obj)
+		if !action_ok {
+			make_error_response(response, .ValidationException,
+				"Invalid TransactItem action")
+			return
+		}
+		append(&actions, action)
+	}
+
+	// Execute transaction
+	result, tx_err := dynamodb.transact_write_items(engine, actions[:])
+	defer dynamodb.transact_write_result_destroy(&result)
+
+	switch tx_err {
+	case .None:
+		response_set_body(response, transmute([]byte)string("{}"))
+
+	case .Cancelled:
+		// Build TransactionCanceledException response
+		builder := strings.builder_make()
+		strings.write_string(&builder, `{"__type":"com.amazonaws.dynamodb.v20120810#TransactionCanceledException","message":"Transaction cancelled, please refer cancellation reasons for specific reasons [`)
+
+		for reason, i in result.cancellation_reasons {
+			if i > 0 {
+				strings.write_string(&builder, ", ")
+			}
+			strings.write_string(&builder, reason.code)
+		}
+
+		strings.write_string(&builder, `]","CancellationReasons":[`)
+
+		for reason, i in result.cancellation_reasons {
+			if i > 0 {
+				strings.write_string(&builder, ",")
+			}
+			fmt.sbprintf(&builder, `{{"Code":"%s","Message":"%s"}}`, reason.code, reason.message)
+		}
+
+		strings.write_string(&builder, "]}")
+
+		response_set_status(response, .Bad_Request)
+		resp_body := strings.to_string(builder)
+		response_set_body(response, transmute([]byte)resp_body)
+
+	case .Validation_Error:
+		make_error_response(response, .ValidationException,
+			"Transaction validation failed")
+
+	case .Internal_Error:
+		make_error_response(response, .InternalServerError,
+			"Internal error during transaction")
+	}
+}
+
+// Parse a single TransactItem action from JSON
+@(private = "file")
+parse_transact_write_action :: proc(obj: json.Object) -> (dynamodb.Transact_Write_Action, bool) {
+	action: dynamodb.Transact_Write_Action
+	action.expr_attr_values = make(map[string]dynamodb.Attribute_Value)
+
+	// Try Put
+	if put_val, has_put := obj["Put"]; has_put {
+		put_obj, put_ok := put_val.(json.Object)
+		if !put_ok {
+			return {}, false
+		}
+		action.type = .Put
+		return parse_transact_put_action(put_obj, &action)
+	}
+
+	// Try Delete
+	if del_val, has_del := obj["Delete"]; has_del {
+		del_obj, del_ok := del_val.(json.Object)
+		if !del_ok {
+			return {}, false
+		}
+		action.type = .Delete
+		return parse_transact_key_action(del_obj, &action)
+	}
+
+	// Try Update
+	if upd_val, has_upd := obj["Update"]; has_upd {
+		upd_obj, upd_ok := upd_val.(json.Object)
+		if !upd_ok {
+			return {}, false
+		}
+		action.type = .Update
+		return parse_transact_update_action(upd_obj, &action)
+	}
+
+	// Try ConditionCheck
+	if cc_val, has_cc := obj["ConditionCheck"]; has_cc {
+		cc_obj, cc_ok := cc_val.(json.Object)
+		if !cc_ok {
+			return {}, false
+		}
+		action.type = .Condition_Check
+		return parse_transact_key_action(cc_obj, &action)
+	}
+
+	return {}, false
+}
+
+// Parse common expression fields from a transact action object
+@(private = "file")
+parse_transact_expression_fields :: proc(obj: json.Object, action: ^dynamodb.Transact_Write_Action) {
+	// ConditionExpression
+	if ce_val, found := obj["ConditionExpression"]; found {
+		if ce_str, str_ok := ce_val.(json.String); str_ok {
+			action.condition_expr = strings.clone(string(ce_str))
+		}
+	}
+
+	// ExpressionAttributeNames
+	if ean_val, found := obj["ExpressionAttributeNames"]; found {
+		if ean_obj, ean_ok := ean_val.(json.Object); ean_ok {
+			names := make(map[string]string)
+			for key, val in ean_obj {
+				if str, str_ok := val.(json.String); str_ok {
+					names[strings.clone(key)] = strings.clone(string(str))
+				}
+			}
+			action.expr_attr_names = names
+		}
+	}
+
+	// ExpressionAttributeValues
+	if eav_val, found := obj["ExpressionAttributeValues"]; found {
+		if eav_obj, eav_ok := eav_val.(json.Object); eav_ok {
+			for key, val in eav_obj {
+				attr, attr_ok := dynamodb.parse_attribute_value(val)
+				if attr_ok {
+					action.expr_attr_values[strings.clone(key)] = attr
+				}
+			}
+		}
+	}
+}
+
+// Parse a Put transact action
+@(private = "file")
+parse_transact_put_action :: proc(
+	obj: json.Object,
+	action: ^dynamodb.Transact_Write_Action,
+) -> (dynamodb.Transact_Write_Action, bool) {
+	// TableName
+	tn_val, tn_found := obj["TableName"]
+	if !tn_found {
+		return {}, false
+	}
+	tn_str, tn_ok := tn_val.(json.String)
+	if !tn_ok {
+		return {}, false
+	}
+	action.table_name = strings.clone(string(tn_str))
+
+	// Item
+	item_val, item_found := obj["Item"]
+	if !item_found {
+		return {}, false
+	}
+	item, item_ok := dynamodb.parse_item_from_value(item_val)
+	if !item_ok {
+		return {}, false
+	}
+	action.item = item
+
+	// Expression fields
+	parse_transact_expression_fields(obj, action)
+
+	return action^, true
+}
+
+// Parse a Delete or ConditionCheck transact action (both use Key)
+@(private = "file")
+parse_transact_key_action :: proc(
+	obj: json.Object,
+	action: ^dynamodb.Transact_Write_Action,
+) -> (dynamodb.Transact_Write_Action, bool) {
+	// TableName
+	tn_val, tn_found := obj["TableName"]
+	if !tn_found {
+		return {}, false
+	}
+	tn_str, tn_ok := tn_val.(json.String)
+	if !tn_ok {
+		return {}, false
+	}
+	action.table_name = strings.clone(string(tn_str))
+
+	// Key
+	key_val, key_found := obj["Key"]
+	if !key_found {
+		return {}, false
+	}
+	key, key_ok := dynamodb.parse_item_from_value(key_val)
+	if !key_ok {
+		return {}, false
+	}
+	action.key = key
+
+	// Expression fields
+	parse_transact_expression_fields(obj, action)
+
+	return action^, true
+}
+
+// Parse an Update transact action
+@(private = "file")
+parse_transact_update_action :: proc(
+	obj: json.Object,
+	action: ^dynamodb.Transact_Write_Action,
+) -> (dynamodb.Transact_Write_Action, bool) {
+	// TableName
+	tn_val, tn_found := obj["TableName"]
+	if !tn_found {
+		return {}, false
+	}
+	tn_str, tn_ok := tn_val.(json.String)
+	if !tn_ok {
+		return {}, false
+	}
+	action.table_name = strings.clone(string(tn_str))
+
+	// Key
+	key_val, key_found := obj["Key"]
+	if !key_found {
+		return {}, false
+	}
+	key, key_ok := dynamodb.parse_item_from_value(key_val)
+	if !key_ok {
+		return {}, false
+	}
+	action.key = key
+
+	// Expression fields (must be parsed before UpdateExpression so attr values are available)
+	parse_transact_expression_fields(obj, action)
+
+	// UpdateExpression
+	ue_val, ue_found := obj["UpdateExpression"]
+	if !ue_found {
+		return {}, false
+	}
+	ue_str, ue_ok := ue_val.(json.String)
+	if !ue_ok {
+		return {}, false
+	}
+
+	plan, plan_ok := dynamodb.parse_update_expression(
+		string(ue_str), action.expr_attr_names, action.expr_attr_values,
+	)
+	if !plan_ok {
+		return {}, false
+	}
+	action.update_plan = plan
+
+	return action^, true
+}
+
+// ============================================================================
+// TransactGetItems Handler
+//
+// Request format:
+// {
+//   "TransactItems": [
+//     {
+//       "Get": {
+//         "TableName": "...",
+//         "Key": { ... },
+//         "ProjectionExpression": "...",          // optional
+//         "ExpressionAttributeNames": { ... }     // optional
+//       }
+//     }
+//   ]
+// }
+// ============================================================================
+
+handle_transact_get_items :: proc(
+	engine: ^dynamodb.Storage_Engine,
+	request: ^HTTP_Request,
+	response: ^HTTP_Response,
+) {
+	data, parse_err := json.parse(request.body, allocator = context.allocator)
+	if parse_err != nil {
+		make_error_response(response, .SerializationException, "Invalid JSON")
+		return
+	}
+	defer json.destroy_value(data)
+
+	root, root_ok := data.(json.Object)
+	if !root_ok {
+		make_error_response(response, .SerializationException, "Request must be an object")
+		return
+	}
+
+	transact_items_val, found := root["TransactItems"]
+	if !found {
+		make_error_response(response, .ValidationException, "Missing TransactItems")
+		return
+	}
+
+	transact_items, ti_ok := transact_items_val.(json.Array)
+	if !ti_ok {
+		make_error_response(response, .ValidationException, "TransactItems must be an array")
+		return
+	}
+
+	if len(transact_items) == 0 {
+		make_error_response(response, .ValidationException,
+			"TransactItems must contain at least one item")
+		return
+	}
+
+	if len(transact_items) > 100 {
+		make_error_response(response, .ValidationException,
+			"Member must have length less than or equal to 100")
+		return
+	}
+
+	// Parse each get action
+	actions := make([dynamic]dynamodb.Transact_Get_Action)
+	defer {
+		for &action in actions {
+			dynamodb.transact_get_action_destroy(&action)
+		}
+		delete(actions)
+	}
+
+	for elem in transact_items {
+		elem_obj, elem_ok := elem.(json.Object)
+		if !elem_ok {
+			make_error_response(response, .ValidationException,
+				"Each TransactItem must be an object")
+			return
+		}
+
+		get_val, has_get := elem_obj["Get"]
+		if !has_get {
+			make_error_response(response, .ValidationException,
+				"TransactGetItems only supports Get actions")
+			return
+		}
+
+		get_obj, get_ok := get_val.(json.Object)
+		if !get_ok {
+			make_error_response(response, .ValidationException,
+				"Get action must be an object")
+			return
+		}
+
+		action, action_ok := parse_transact_get_action(get_obj)
+		if !action_ok {
+			make_error_response(response, .ValidationException,
+				"Invalid Get action")
+			return
+		}
+		append(&actions, action)
+	}
+
+	// Execute transaction get
+	result, tx_err := dynamodb.transact_get_items(engine, actions[:])
+	defer dynamodb.transact_get_result_destroy(&result)
+
+	if tx_err != .None {
+		make_error_response(response, .InternalServerError,
+			"Transaction get failed")
+		return
+	}
+
+	// Build response
+	builder := strings.builder_make(context.allocator)
+	defer strings.builder_destroy(&builder)
+
+	strings.write_string(&builder, `{"Responses":[`)
+
+	for maybe_item, i in result.items {
+		if i > 0 {
+			strings.write_string(&builder, ",")
+		}
+
+		if item, has_item := maybe_item.?; has_item {
+			strings.write_string(&builder, `{"Item":`)
+			dynamodb.serialize_item_to_builder(&builder, item)
+			strings.write_string(&builder, `}`)
+		} else {
+			strings.write_string(&builder, "{}")
+		}
+	}
+
+	strings.write_string(&builder, "]}")
+
+	// Clone the string or we gonna have issues again
+	resp_body := strings.clone(strings.to_string(builder))
+	response_set_body(response, transmute([]byte)resp_body)
+}
+
+// Parse a single TransactGetItems Get action
+@(private = "file")
+parse_transact_get_action :: proc(obj: json.Object) -> (dynamodb.Transact_Get_Action, bool) {
+	action: dynamodb.Transact_Get_Action
+
+	// TableName
+	tn_val, tn_found := obj["TableName"]
+	if !tn_found {
+		return {}, false
+	}
+	tn_str, tn_ok := tn_val.(json.String)
+	if !tn_ok {
+		return {}, false
+	}
+	action.table_name = strings.clone(string(tn_str))
+
+	// Key
+	key_val, key_found := obj["Key"]
+	if !key_found {
+		return {}, false
+	}
+	key, key_ok := dynamodb.parse_item_from_value(key_val)
+	if !key_ok {
+		return {}, false
+	}
+	action.key = key
+
+	// ProjectionExpression (optional)
+	if pe_val, pe_found := obj["ProjectionExpression"]; pe_found {
+		if pe_str, pe_ok := pe_val.(json.String); pe_ok {
+			// Parse ExpressionAttributeNames for projection
+			attr_names: Maybe(map[string]string) = nil
+			if ean_val, ean_found := obj["ExpressionAttributeNames"]; ean_found {
+				if ean_obj, ean_ok := ean_val.(json.Object); ean_ok {
+					names := make(map[string]string, allocator = context.temp_allocator)
+					for key_str, val in ean_obj {
+						if str, str_ok := val.(json.String); str_ok {
+							names[key_str] = string(str)
+						}
+					}
+					attr_names = names
+				}
+			}
+
+			parts := strings.split(string(pe_str), ",")
+			paths := make([dynamic]string)
+			for part in parts {
+				trimmed := strings.trim_space(part)
+				if len(trimmed) == 0 {
+					continue
+				}
+				resolved, res_ok := dynamodb.resolve_attribute_name(trimmed, attr_names)
+				if !res_ok {
+					delete(paths)
+					dynamodb.item_destroy(&action.key)
+					return {}, false
+				}
+				append(&paths, strings.clone(resolved))
+			}
+			action.projection = paths[:]
+		}
+	}
+
+	return action, true
+}
+
+// ============================================================================
+// UPDATED_NEW / UPDATED_OLD Filtering Helper
+//
+// DynamoDB ReturnValues semantics:
+//   ALL_NEW      → all attributes of the item after the update
+//   ALL_OLD      → all attributes of the item before the update
+//   UPDATED_NEW  → only the attributes that were modified, with new values
+//   UPDATED_OLD  → only the attributes that were modified, with old values
+//
+// This filters an item to only include the attributes touched by the
+// UpdateExpression (the "modified paths").
+// ============================================================================
+
+filter_updated_attributes :: proc(
+	item: dynamodb.Item,
+	plan: ^dynamodb.Update_Plan,
+) -> dynamodb.Item {
+	modified_paths := dynamodb.get_update_plan_modified_paths(plan)
+	defer delete(modified_paths)
+
+	return dynamodb.filter_item_to_paths(item, modified_paths)
+}