Dynamodb Toolbox Patterns

If you're building TypeScript services on DynamoDB and want strict type safety without fighting the SDK, this gives you working patterns for DynamoDB-Toolbox v2. It covers the full `.build()` command workflow for CRUD, query and scan access patterns with GSIs, batch and transaction operations, and single-table design with computed keys. The examples show real schema modeling with transforms, defaults, and complex attributes like maps and lists. Most useful when you're past the proof-of-concept stage and need production patterns that keep your keys consistent and your access patterns explicit. Includes guidance on avoiding common pitfalls like table scans in request paths and misusing transactions.