By default, Function Compute instances are used in the on-demand mode. On-demand instances are automatically created upon requests. On-demand instances are destroyed when no requests are sent for processing for a period of time (usually 3 to 5 minutes). When you invoke an on-demand instance for the first time, you must wait for the cold start of the instance to complete. Therefore, functions that are infrequently used take a longer period of time to invoke.