When you increase the number of Realm clients in your deployment, they use a connection pool to share and reuse the connections that are visible in Atlas. The pool size is limited to the maximum number of connections allowed by your Atlas cluster, and the cluster will not accept new connections when that maximum is reached.

Note that Realm will create a connection and keep it open as long as the connection is active. Realm will release the connection after a period of inactivity.

Before moving a Realm app to production, we recommend testing your configuration in a staging Atlas environment by simulating your workload and connection attempts.