AWS RDS new db.r5 class not avalibale for existing database cluster - All sizes of instance not available for new R5 class in exiting cluster Aurora

Question

I am using aws RDS with class db.r5.12xlarge, so when I am trying to downgrade my database to lower size then I am not able to find all sizes of db.r5 class. I have a requirement to set the database with size db.r5.8xlarge but this option is not showing while modifying the DB instance.

So these are available classes for my existing RDS cluster.

But when I am trying to create a new Database then I can see all sizes of R5 classes.

Here is the structure of my RDS cluster. I am using Aurora with MySql compatibility.

Answer 1

I ran into this same issue when trying to scale up an instance. Long story short, there's a compatibility matrix for instance classes and DB engines. Buried within you'll find that MariaDB, MySQL, or Postgres are not supported by the db.r5.8xlarge class. So much for instance size flexibility with reserved instances...

https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/Concepts.DBInstanceClass.html