Just trying to get my head firmly around the RDS session number and associated performance/saturation. It says a session is any request waiting on a response from the server, so I am wondering if that's equivalent to selecting all from pg_stat_activity where state is active, and this would include all concurrent parallel workers, maintenance stuff, etc.
If you are referring to something in the RDS documentation or monitoring, could you provide a link to it, or an excerpt of it?