RDS MySQL Read Replicas: How They Affect Your RI Strategy

This article is a practical guide on RDS MySQL read replicas and Reserved Instances: it explains that read replicas are billed as regular Single‑AZ DB instances and require one RI per running instance (region and deployment type must match), highlights the cross‑region RI gap and data transfer costs, provides sizing and replication‑lag guidance before purchasing RIs, lists costs not covered by RIs (burst credits, storage, cross‑region transfer, extended support), and concludes with a step‑by‑step RI purchase checklist and tooling notes for optimization.