We're going to show you how to promote an RDS read-replica to be a primary instance. There are a few reasons you might like to do this:
- To handle a table migration that would typically cause a large amount of downtime, especially when messing with columns or indexes
- Because you need to implement sharding
- Recovery from failure, should you choose not to deploy your existing primary in multi-AZ mode (not recommended)
You're going to need the unique ID, which has been assigned to an RDS read-replica. If you followed the previous Creating a database with automatic failover, and Creating a database read-replica recipes, then you'll be all set.
It's also a good idea to have backups enabled on this read-replica prior to promoting it. This shortens the promotion process because you won't need to wait for a backup to be taken. You'll want to set the backup retention period to a value between 1 and 8.