The timer function apps run at configurable intervals. The time at which the function should execute is defined through a CRON expression. The CRON expression is composed of six fields: {second} {minute} {hour} {day} {month} {day of the week}. These fields, separated by white space, can contain any of the allowed values with various combinations of the allowed characters for that field. For example, to trigger your function every 15 minutes, your scheduling CRON expression should be set to: 0 */15 * * * *.

Timer function apps are generally used to send information to other systems. They don't generally return information and write the progress of the operation to logs. This category of functions is typically built to clean up or manage reconcile or manage data at regular intervals. Timer functions are also used for checking the health of other services by pinging them at regular intervals. Just like any other category of functions, these functions can be combined with other functions to develop a complex scenario.