Can't connect to MySQL server on '*.cluster-*.us-east-8.rds.amazonaws.com' error

Hi,

i have a python app that runs on a ec2 and connects to a RDS MySQL Database on an Aurora Instance (not Aurora serverless). It works if a small amount of users use it. But once like 20+ users hit it at the same time i get the error Can't connect to MySQL server on '*****.cluster-*******.us-east-8.rds.amazonaws.com' error.

I read that the max connections could be responsible for that. But from what i read that fully depends on the RAM of the RDS.

Therefore i tried upgrading from a t3 large to a r5 large. But that sadly did not make a difference.

BUT: My application is build in such a way that even when multiple users use it there is basically only the 1 single application making the calls to the database. And i read somewhere that there is also a second max connections per user variable that could be the cause of it. I sadly did not find where that is tho.

So my question in general is if someone maybe has experience with getting this error when they use the RDS too hard and what could potentialy be done to troubleshoot (to find the cause) and then of course fix it so it can handle a larger amount of users