A package delivery company runs an application on Amazon EC2 instances with an Amazon Aurora MySQL DB cluster. As the application grows, EC2 usage increases only slightly while DB cluster usage increases much faster. Adding a read replica reduces DB load only briefly; load continues to rise. The operations increasing DB usage are repeated read statements related to delivery details. The company needs to reduce the impact of repeated reads on the DB cluster MOST cost-effectively. Which solution meets this requirement?

Implementing an Amazon ElastiCache for Redis cluster is the most cost-effective solution because it provides an in-memory cache for frequently accessed data, significantly reducing the load on the Aurora MySQL DB cluster from repeated read statements. This offloads the database and improves application performance without scaling the database itself. Adding another read replica would only temporarily alleviate the load, as the underlying issue of repeated reads hitting the database persists and will eventually overwhelm the new replica. Configuring Aurora Auto Scaling for read replicas would scale the replicas but not address the root cause of excessive read requests, leading to higher costs. Modifying the DB cluster to have multiple writer instances is incorrect because the problem is with read operations, not write operations, and Aurora MySQL is designed with a single writer instance per cluster.