I spun up two RDS instances in the same VPC. Both are postgresql.
While the m4.xlarge one has multi-AZ enabled and is encrypted. The t2.micro has either. That is the only difference between the two instances. It is strange that t2.micro instance can be stopped but m4.xlarge can't. The "stop" option is grayed out for m4.xlarge.
Why can't I stop this one? Does it have to do with the multi-AZ thing?
You can't stop a DB instance that is in a Multi-AZ deployment.
http://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER_StopInstance.html
Modify the instance so that it is no longer Multi-AZ. After this modification is complete, you should be able to stop it. You can switch it back to being Multi-AZ after it is restarted.
Now it's possible to stop RDS in Multi-AZ mode
https://aws.amazon.com/about-aws/whats-new/2018/10/amazon-rds-stop-and-start-of-multi-az-instances/
Also note it can only be stopped for up to 7 days
You can stop a database instance for up to 7 days at a time. After 7 days, it will be automatically started
You can stop RDS DB instances except for SQL Server DB instance in a Multi-AZ configuration. There are some limitations you should know about this:
Limitations The following are some limitations to stopping and starting a DB instance:
You can't stop a DB instance that has a read replica, or that is a read replica.
You can't stop an Amazon RDS for SQL Server DB instance in a Multi-AZ configuration.
You can't modify a stopped DB instance.
You can't delete an option group that is associated with a stopped DB instance.
You can't delete a DB parameter group that is associated with a stopped DB instance.
