The correct answer is: Use Amazon ElastiCache for Redis to cache frequently accessed data and reduce repeated reads from the RDS databases.

Amazon ElastiCache for Redis is a highly available, in-memory data store that can cache frequent queries or computation results. This reduces the load on the RDS database by serving repetitive reads from the cache. Redis supports complex data types and offers features like replication, automatic failover, and persistence, making it ideal for high-performance and highly available caching scenarios.

Why the other options are incorrect:

Adding Amazon RDS read replicas can distribute read traffic but doesnt eliminate redundant queries or optimize performance for repeatable lookups. Also, read replicas still introduce some latency and potential replication lag, and they do not provide the same in-memory speed benefits as a caching layer.

Amazon Route 53 DNS caching is related to DNS resolution and routing, not application-level data caching or database optimization. It would have no effect on reducing RDS read traffic.

Using Amazon ElastiCache for Memcached is a valid option for simple key-value caching, but Memcached lacks features such as persistence, advanced data structures, and built-in replication for high availability. Redis is the preferred choice when high availability and complex caching are needed.

Why this question matters: This question tests your ability to optimize data access patterns and reduce pressure on relational databases using appropriate AWS services. Choosing between caching and read replicas is a common design decision in performance tuning.

Tip: When you see repeated reads, latency issues, or unnecessary load on RDS, consider caching first. Use Redis for more advanced use cases requiring HA, replication, or data persistence. Memcached is suitable for simple, ephemeral, and non-critical caching.

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