I recently needed to perform a major version upgrade to several AWS Aurora instances, however ran into issues when trying to create a new instance by restoring from a snapshot.
I won’t go into how to perform the upgrade, that’s available in the AWS docs here: Upgrading AWS Aurora DB Instance. I will share a very helpful piece of information I found in this recent Stack Overflow thread, thank you to the poster 🙏.
Apparently there is a known issue with some RDS instance types that won’t allow you to upgrade smoothly. For us, we were trying to upgrade an existing db.r5.large instance from Postgres 12 to Postgres 13. The upgrade didn’t work until we changed our new target instance to an db.r6g.large instead. By simply changing the instance type we were able to perform the upgrade from within the AWS console.