AWS Certified Solutions Architect – Associate (SAA-C03) — Question 455

A company has a mobile chat application with a data store based in Amazon DynamoDB. Users would like new messages to be read with as little latency as possible. A solutions architect needs to design an optimal solution that requires minimal application changes.

Which method should the solutions architect select?

Answer options

• A. Configure Amazon DynamoDB Accelerator (DAX) for the new messages table. Update the code to use the DAX endpoint.
• B. Add DynamoDB read replicas to handle the increased read load. Update the application to point to the read endpoint for the read replicas.
• C. Double the number of read capacity units for the new messages table in DynamoDB. Continue to use the existing DynamoDB endpoint.
• D. Add an Amazon ElastiCache for Redis cache to the application stack. Update the application to point to the Redis cache endpoint instead of DynamoDB.

Correct answer: A

Explanation

Amazon DynamoDB Accelerator (DAX) is an API-compatible, in-memory cache that reduces DynamoDB read latency from milliseconds to microseconds with minimal application changes, as it only requires updating the database client to point to the DAX endpoint. In contrast, implementing Amazon ElastiCache for Redis would require significant application code changes to handle cache-aside logic. Increasing RCUs or utilizing read replicas would not provide the microsecond read latencies that an in-memory cache like DAX delivers.