Each task has three associated times:
createdis the time the task was created;
deadlineis the time by which the task must be completed; and
expiresis the time after which all record of the task and its runs will be deleted.
The deadline exists to ensure that tasks do not remain pending forever. It is
usually set to one day after
created, on the assumption that running the task
more than a day later is not useful.
Task expiration ensures that tasks are not stored indefinitely, thereby controlling storage costs. Expiration is often set to one year after creation, but for common tasks, tasks which produce large artifacts, or tasks which are unlikely to be useful later, a much shorter expiration is appropriate.