https://aws.amazon.com/premiumsupport/knowledge-center/dynamodb-high-latency/

Amazon DynamoDB Accelerator (DAX) is a fully managed in-memory cache for DynamoDB that improves the performance of DynamoDB tables by up to 10 times and provides microsecond level of response time at any scale. It is compatible with DynamoDB API operations and requiresminimal code changes to use1. By configuring DAX for the new messages table, the solution can reduce the latency for reading new messages with minimal application changes.

B. Add DynamoDB read repticas to handle the increased read load. Update the application to point to the read endpoint for the read replicas. This solution will not work, as DynamoDB does not support read replicas as a feature. Read replicas are available for Amazon RDS, not for DynamoDB2.

C. Double the number of read capacity units for the new messages table in DynamoDB. Continue to use the existing DynamoDB endpoint. This solution will not meet the requirement ofreading new messages with aslittle latency as possible, as increasing the read capacity units will only increase the throughput of DynamoDB, not the performance or latency3.

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. This solution will not meet the requirement of minimal application changes, as adding ElastiCache for Redis will require significant code changes to implement caching logic, such as querying cache first, updating cache after writing to DynamoDB, and invalidating cache when needed.

Reference URL: https://aws.amazon.com/dynamodb/dax/