A company is moving an on-premises database to Amazon RDS for MySQL. The workload is read-heavy and the company wants to refactor the application for optimal read performance. Which option achieves the best read scaling with the LEAST current and future effort?

Deploying Amazon RDS with read replicas is the most effective solution for read-heavy workloads. Read replicas provide independent endpoints for read traffic, offloading the primary instance and improving read performance and scalability. Modifying the application to direct read queries to these endpoints is a standard practice for optimizing read-heavy applications. Using a Multi-AZ deployment primarily provides high availability and disaster recovery, not read scaling. Increasing connection numbers or pool size won't scale reads beyond the primary instance's capacity. Directing queries to a Multi-AZ standby instance is not supported and would disrupt its role in failover. Using open-source replication to an EC2 instance introduces significant operational overhead for management, patching, and scaling, which goes against the goal of "least effort." Additionally, querying by IP address is less flexible and resilient than using RDS endpoints.