Implementing read replicas using Amazon RDS allows you to handle read-heavy database workloads by creating one or more read-only copies of your database. This approach offloads read queries from the primary database, thus enhancing performance and availability without impacting the primary database's performance. Although the other options might appear feasible, they either do not address the requirement (such as Data Lifecycle Policy, which is related to data retention rather than read capacity) or are less efficient for the needs stated (like Multi-AZ deployment, which primarily addresses high availability and failover rather than read scalability). Caching with Amazon ElastiCache could improve read performance, but for read-heavy relational database applications, read replicas are purpose-built to serve this requirement and are the most cost-effective solution.