Overview
Read replicas are used to scale the read capacity of a relational database. The primary instance handles all writes (INSERT, UPDATE, DELETE), and changes are asynchronously replicated to one or more read replicas.
Key Benefits
- Scalability: Offloads read-heavy workloads from the primary instance.
- Performance: Replicas can be placed in different regions to serve local users with lower latency.
- Availability: Can be promoted to a primary instance in some disaster recovery scenarios.
Considerations
- Replication Lag: Because replication is asynchronous, there may be a slight delay before a write on the primary appears on the replica.
- Read-Only: Replicas cannot accept write operations directly.