The isValid method in a JDBC connection is used by connection pools to determine whether a connection is safe to hand out to an application. Executing a query each time for this is not very efficient for Cloud Spanner, as the Cloud Spanner JDBC connection is just a wrapper around the client library, and does not implement a physical connection with Cloud Spanner. This means that loss of network connectivity is 'all-or-nothing'; if the network connection to Cloud Spanner has been lost, then it will apply to all JDBC connections, and not only a specific one. There is therefore no point in repeatedly executing a query on Cloud Spanner to check whether a connection is valid or not.