Comment by darkwater

There is still a max capped on the instance size [1] (well, RAM available) although now that I'm checking it again I swear it was different last time I read it. Anyway I did totally had issues with big replicated monoliths with their own connection pool (i.e. old Rails) maxing out connections on RDS.

[1] https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_...