A company hosts a web app on RDS for MySQL with a primary DB instance and five read replicas. Replicas must lag no more than 1 second behind the primary. The database runs scheduled stored procedures, and replicas experience more lag during peak load. The solutions architect must reduce replication lag as much as possible while minimizing application code changes and ongoing operational overhead. Which solution meets these requirements?

Migrating to Amazon Aurora MySQL with Aurora Replicas is the best solution. Aurora is designed for high performance and scalability, offering up to 15 read replicas with very low replication lag (typically milliseconds), significantly better than standard RDS for MySQL. Aurora Auto Scaling automatically adjusts replica capacity, minimizing operational overhead. Replacing stored procedures with Aurora MySQL native functions ensures compatibility and leverages Aurora's optimized engine. Deploying ElastiCache for Redis would require significant application code changes to implement caching logic, which the question aims to minimize. Migrating to EC2 instances increases operational overhead for database management and doesn't inherently guarantee lower replication lag than Aurora. Migrating to DynamoDB is a NoSQL solution, requiring substantial application re-architecture and code changes, as well as a complete rewrite of stored procedures, which is not ideal for minimizing changes.