Patterns and best practices for Amazon DynamoDB data modeling and access patterns. Use when the user asks about DynamoDB table design, single-table design, GSIs, multi-attribute composite keys, one-to-many relationships, cost optimization, or Terraform DynamoDB resources. Triggers on: DynamoDB, single-table design, GSI, partition key, sort key, access patterns, filter expressions, TTL, vertical sharding, composite keys, multi-attribute keys.