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Cloud Computing · Intermediate

Read Replica

Asynchronously replicated, read-only copy of a database used to offload read traffic and support disaster recovery.

Definition

Read replicas receive asynchronous updates from a primary database and serve read-only queries, increasing read throughput. They can be in the same or another region (cross-region replicas) and can be promoted to standalone primaries. Amazon RDS, Aurora, Azure SQL, Cloud SQL and others support them.

Example

Reporting queries are pointed at a read replica so they do not slow the primary transactional workload.

Exam tip

Replication lag means replicas can return stale data; they are not a substitute for synchronous Multi-AZ failover.

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