I have an RDS instance with the below configuration.
create role role1 login noinheritance;
grant rds_superuser to rdsdba;
grant rdsdba to role1
In this case role1 is able to do all administrative operations, without the need of switching to rdsdba.
Is this expected?
I do not find any document which says that inheritance does not work with roles which have superuser role granted to it. Note that rdsdba is not a superuser in itself, but only has a role which is superuser.
