Answer: Use Amazon ElastiCache for Redis.

## Explanation **Correct Answer: B - Use Amazon ElastiCache for Redis** **Why this is correct:** 1. **Problem Analysis**: The company has a batch application causing high read loads on RDS databases. The goal is to reduce database reads while maintaining high availability. 2. **Amazon ElastiCache for Redis Solution**: - **Caching Mechanism**: Redis is an in-memory data store that can cache frequently accessed data, dramatically reducing the number of database reads. - **High Availability**: Amazon ElastiCache for Redis supports Multi-AZ deployments with automatic failover, ensuring high availability. - **Performance**: In-memory caching provides sub-millisecond latency for read operations. - **Data Persistence**: Redis supports data persistence, which is important for batch applications that may need to recover from failures. 3. **Comparison with Other Options**: - **Option A (RDS Read Replicas)**: While read replicas can help distribute read traffic, they don't actually reduce the total number of database reads - they just distribute them across multiple instances. The data still needs to be read from disk. - **Option C (Route 53 DNS Caching)**: This is completely unrelated to database read reduction. Route 53 is a DNS service, not a database caching solution. - **Option D (ElastiCache for Memcached)**: While Memcached is also a caching solution, Redis is generally preferred for scenarios requiring high availability and data persistence. Redis supports more advanced features like replication, persistence, and data structures that are valuable for batch applications. 4. **Implementation Benefits**: - **Reduced Database Load**: Frequently accessed data can be served from cache - **Improved Performance**: In-memory access is much faster than disk-based database reads - **Scalability**: ElastiCache can scale horizontally to handle increased load - **Cost Reduction**: Reduced database load can lead to smaller RDS instance requirements **Key AWS Services Mentioned**: - **Amazon EC2**: Compute instances running the batch application - **Amazon RDS**: Relational database service - **Amazon ElastiCache**: Managed caching service (Redis/Memcached) **Best Practice**: For read-heavy applications with high availability requirements, Amazon ElastiCache for Redis with Multi-AZ deployment is the recommended approach to reduce database load while maintaining system resilience.

Author: LeetQuiz Editorial Team