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2-read-replicas.md

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Read Replicas

  • A read replica is a read-only copy of your primary database

  • When your application does a query, it would query the read replica and not your database, reducing load on your database

  • Use for read-heavy workloads - takes the load off your primary database

  • Read replicas can cross different availablity zones or regions

  • Each read replica has it's own DNS endpoint

  • Read replicas can be promoted to be their own databases

    • This breaks replication between the replica and primary database

  • Automatic backups must be enabled to deploy a read replica

  • Multiple read replicas are supported

    • MySQL, MariaDB, PostgreSQL, Oracle and SQL Server
    • Add up to 5 read replicas to each database instance

  • Multi-AZ is for disaster recovery, read replicas are for scaling and improving performance

    • Multi-AZ is an exact copy of your production database
    • Used for disaster recovery
    • RDS will automatically fail over to standby instance in the event of a failure