DynamoDB · NoSQL Key-Value Store

Outcome

• Access PatternsIAM & Access Pattern Thinking
  • Explain the difference between dynamodb:GetItem and dynamodb:Query and why having one doesn't imply the other
  • List the access patterns for a service before designing any table
  • Map each access pattern to a base table key or GSI
  • Explain why IAM policy typos in resource ARNs are undetectable at creation time
• Access PatternsTables, Items, and the Data Model
  • Explain partition key, sort key, and how DynamoDB co-locates items by PK
  • Create a table with GSIs in one CLI call
  • Use PutItem, GetItem, UpdateItem, DeleteItem correctly
  • Use expression attribute names to alias reserved words
  • Explain why PutItem is a full overwrite and when to use UpdateItem instead
  • Explain the cost difference between Query and Scan with --return-consumed-capacity
• Access PatternsSingle-Table Design
  • Explain why single-table design exists and what problem it solves
  • Model multiple entity types using generic PK/SK patterns
  • Use begins_with(SK, prefix) to filter entity types within a partition
  • Explain why # separators prevent SK prefix collisions
  • Explain the difference between FilterExpression and KeyConditionExpression
• Access PatternsGSIs and LSIs
  • Explain when to use a GSI vs an LSI
  • Query a GSI with --index-name and a date range SK condition
  • Add a GSI to an existing table and wait for backfill
  • Explain GSI eventual consistency and why you can't read from a GSI immediately after writing
  • Explain the hot partition problem on low-cardinality GSI PKs
• Access PatternsDynamoDB Streams & TTL
  • Enable TTL and explain why the attribute must be a Number type
  • Enable Streams with NEW_AND_OLD_IMAGES and connect a Lambda consumer
  • Distinguish TTL deletes from application deletes in stream records
  • Explain at-least-once delivery and why stream consumers must be idempotent
  • Explain what happens when a Lambda stream consumer fails repeatedly
• Access PatternsTransactions, Conditional Writes & Capacity
  • Use attribute_not_exists(PK) for idempotent creates
  • Implement optimistic locking with a version attribute
  • Use TransactWriteItems for atomic multi-item writes
  • Explain why transactions cost 2× WCU and when not to use them
  • Explain what ConditionalCheckFailedException means and how to handle it with retry logic
  • Calculate RCU cost for a strongly consistent vs eventually consistent read