Each Aurora has a max connections limit. E.g. “db.t2.small” is around 45 connections. The limit is derived from the instance’s memory size. The larger the memory the bigger the max connection limit. See more info here: https://docs.aws.amazon.com/AmazonRDS/latest/AuroraUserGuide/AuroraMySQL.Managing.Performance.html

If max limit is reached you will not be able to connect. May receive error like this:

com.mysql.jdbc.exceptions.MySQLNonTransientConnectionException: Too many connections

It is possible to manually change the max limit in the “Parameter Groups”. First create a new parameter group (default one cannot be modified). Find the “max_connections” parameter and change the value. The default value looks like this:

GREATEST({log(DBInstanceClassMemory/805306368)45},{log(DBInstanceClassMemory/8187281408)1000})

Then modify db instance and select the new parameter group.

WARNING – changing parameter group will require database to restart. Expect some down time.