Creating cross-Region cascading read replicas with RDS for PostgreSQL - Amazon Relational Database Service
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Creating cross-Region cascading read replicas with RDS for PostgreSQL

RDS for PostgreSQL supports cross-Region cascading read replicas. You can create a cross-Region replica from the source DB instance, and then create same-Region replicas from it. You can also create a same-Region replica from the source DB instance, and then create cross-Region replicas from it.

Create a cross-Region replica and then create same-Region replicas

You can use an RDS for PostgreSQL DB instance with version 14.1 or higher, rpg-db-main, to do the following:

  1. Start with rpg-db-main (US-EAST-1), create the first cross-Region read replica in the chain, read-replica-1 (US-WEST-2).

  2. Using the first cross-Region read-replica-1 (US-WEST-2), create the second read replica in the chain, read-replica-2 (US-WEST-2).

  3. Using read-replica-2, create the third read replica in the chain, read-replica-3 (US-WEST-2).

Create a same-Region replica and then create cross-Region replicas

You can use an RDS for PostgreSQL DB instance with version 14.1 or higher, rpg-db-main, to do the following:

  1. Starting with rpg-db-main (US-EAST-1), create the first read replica in the chain, read-replica-1 (US-EAST-1).

  2. Using read-replica-1 (US-EAST-1), create the first cross-Region read replica in the chain, read-replica-2 (US-WEST-2).

  3. Using read-replica-2 (US-WEST-2), create the third read replica in the chain, read-replica-3 (US-WEST-2).

Limitations in creating cross-Region read replicas

  • A cross-Region cascading chain of database replicas can span a maximum of two Regions, with a maximum of four levels. The four levels include the database source and three read replicas.

Advantages of using cascading read replicas

  • Improved read scalability – By distributing read queries across multiple replicas, cascading replication helps balance the load. This improves performance, especially in read-heavy applications, by reducing the strain on the writer database.

  • Geographical distribution – Cascading replicas can be located in different geographic locations. This reduces latency for users located far from the primary database and provides a local read replica, enhancing performance and user experience.

  • High availability and disaster recovery – In the event of a primary server failure, replicas can be promoted to primary, ensuring continuity. cascading replication further enhances this by providing multiple layers of failover options, improving the overall resilience of the system.

  • Flexibility and modular growth – As the system grows, new replicas can be added at different levels without major reconfiguration of the primary database. This modular approach allows for scalable and manageable growth of the replication setup.

Best practice for using cross-Region read replicas

  • Before promoting a replica, create additional replicas. This will save time, and provide efficient handling of the workload.