Unable to upgrade Aurora 1 / MySQL 5.6 due to different instances in cluster (Blue-Green deployment)

Question

This RDS cluster has 2 different instances db.r5.large and db.r3.large. We understand that the r3 class is no longer supported, but appear to be stuck in an endless loop.

Going though the steps for a Blue Green deployment but we either get an error stating: 
"RDS does not support creating a DB Instance with the following combination: DBInstanceClass=db.r3.large, EngineVersion=5.7.mysql_aurora.2.11.1..."

If we try to upgrade the above instance from db.r3.large to db.r5.large, 
then we get error: "Cannot modify the instance class because there are no  instances of the requested class available in the current instance's availability zone, please try later..." We have tried multiple times over the past few weeks and its clear that this is because the r3 class is deprecated now.

Answer

I would recommend doing the following:
1. Add a reader with db.r5.large.
2. Remove the db.r3.large from the cluster (delete it)
3. Run your blue/green deployment.
This should remove the issue causing instance and your deployment should now run as expected.

Hope this helps.

Unable to upgrade Aurora 1 / MySQL 5.6 due to different instances in cluster (Blue-Green deployment)

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