Working with MySQL read replicas

Following, you can find specific information about working with read replicas on RDS for MySQL. For general information about read replicas and instructions for using them, see Working with DB instance read replicas.

For more information about MySQL read replicas, see the following topics.

Configuring read replicas with MySQL

Before a MySQL DB instance can serve as a replication source, make sure to enable automatic backups on the source DB instance. To do this, set the backup retention period to a value other than 0. This requirement also applies to a read replica that is the source DB instance for another read replica. Automatic backups are supported for read replicas running any version of MySQL. You can configure replication based on binary log coordinates for a MySQL DB instance.

On RDS for MySQL version 5.7.44 and higher MySQL 5.7 versions and RDS for MySQL 8.0.28 and higher 8.0 versions, you can configure replication using global transaction identifiers (GTIDs). For more information, see Using GTID-based replication.

You can create up to 15 read replicas from one DB instance within the same Region. For replication to operate effectively, each read replica should have the same amount of compute and storage resources as the source DB instance. If you scale the source DB instance, also scale the read replicas.

RDS for MySQL supports cascading read replicas. To learn how to configure cascading read replicas, see Using cascading read replicas with RDS for MySQL.

You can run multiple read replica create and delete actions at the same time that reference the same source DB instance. When you perform these actions, stay within the limit of 15 read replicas for each source instance.

A read replica of a MySQL DB instance can't use a lower DB engine version than its source DB instance.

Preparing MySQL DB instances that use MyISAM

If your MySQL DB instance uses a nontransactional engine such as MyISAM, you need to perform the following steps to successfully set up your read replica. These steps are required to make sure that the read replica has a consistent copy of your data. These steps are not required if all of your tables use a transactional engine such as InnoDB.