AWS RDS Replica Promotion Consequence

Question

Hello,

I have a scenario where I need to create a second tier replica for mysql RDS and I want to promote the first read replica as Primary. I need to understand that will this cause my first tier to second tier replication to break.

E.g. R1 is the Primary RDS. R2 is the first read replica(Multi AZ) and R3 is the second replica. If I promote R2 as the primary & thereby it becomes a standalone instance will it cause it's downstream replication to R3 fail or will it continue as is.

Regards,
Sourav

Steve_M · Answer

It would appear so. According to https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_ReadRepl.html (nearly halfway down):

> The promotion process takes a few minutes to complete. When you promote a read replica, replication is stopped and the read replica is rebooted. When the reboot is complete, the read replica is available as a new DB instance.

Note that the document goes on to suggest that putting your setup back to Multi-AZ again is a manual task:

> 4. (Optional) Modify the new DB instance to be a Multi-AZ deployment. For more information, see Modifying an Amazon RDS DB instance and Configuring and managing a Multi-AZ deployment.

AWS RDS Replica Promotion Consequence

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