PostgreSQL Read Replicas

A read replica is a separate instance of your PostgreSQL database that only allows read access. As you write data to your primary instance, Render asynchronously replicates those changes to your read replica:

A read replica can reduce load on your primary instance and make one-off queries safer. They’re great for analysis tools that don’t need to write data, or for running computationally expensive queries without affecting the performance of your primary instance.

Requirements

You can create a read replica for any PostgreSQL database on the Standard instance type or higher. Each primary instance supports up to one read replica.

A read replica instance always uses the same instance type as its primary instance and is billed accordingly.

Setup

Go to your database’s Info page in the Render Dashboard and click Add Read Replica:

A confirmation dialog appears. If you confirm, Render spins up the replica instance and starts copying over data from the primary instance. That’s it! Your read replica should become available within a few minutes. If it takes longer, please contact us.

After your read replica becomes available, you can connect to it just like you do your primary instance, using its internal or external connection URL.

Performance

Changes to your primary instance are reflected by your read replica after a short delay. This means the replica is best suited to use cases that don’t require instant access to the most recent data possible.

The length of this delay depends on your primary instance’s load. You can monitor this from the primary instance’s Metrics page, under Replication Lag.

Read replicas vs. high availability

A read replica database instance is different from a standby instance that’s used for high availability. Read replicas help decrease load on your primary instance, and they’re safer for one-off and expensive queries. In contrast, a standby instance helps reduce downtime in the event of instance failure.