An application needs to process 100,000 transactions per second with sub-millisecond latency. Which caching solution should be used?

Correct answer: Amazon ElastiCache for Redis

Option D is correct because Amazon ElastiCache for Redis is the appropriate choice for an application requiring 100,000 transactions per second with sub-millisecond latency; Redis is an in-memory data structure store that delivers single-digit microsecond response times, supports complex data types and atomic operations, and scales to handle millions of requests per second with clustering, making it the standard AWS solution for extreme low-latency caching workloads. Option A is incorrect because Amazon CloudFront is a Content Delivery Network (CDN) that caches static and dynamic content at edge locations to reduce latency for end users globally, but it is not designed for application-tier transaction caching at the database layer. Option B is incorrect because DynamoDB DAX (DynamoDB Accelerator) is an in-memory cache specifically for DynamoDB tables and only benefits read-heavy DynamoDB workloads; it is not a general-purpose caching layer for arbitrary applications. Option C is incorrect because S3 Transfer Acceleration speeds up uploads and downloads to Amazon S3 by routing traffic through AWS edge locations and the AWS backbone network, and has no relevance to application-tier caching or transactional latency.