JDBC connections use the session pool implementation in the Java client library, and all connections in one JVM to the same database using the same credentials will share a session pool. It is however currently not possible to configure the minimum and maximum number of sessions in this session pool. This could lead to session pool exhaustion in extreme high load situations when Cloud Spanner is used through JDBC.

The JDBC connection URL should therefore support specifying a min and max for the number of sessions in the pool.