Schedules: Cron, Interval, Event

Concepts covered: paScheduleTypes, paCatchupMode

Every DAG has a schedule. The schedule decides when a run starts. Three forms cover almost every production case: cron expressions for repeated wall-clock times, intervals for relative cadences (every fifteen minutes, every hour), and event triggers for runs that start when something external happens. A modern orchestrator supports all three, and the right choice depends on the source's behavior, not on engineer preference. Cron Expressions A cron expression is five fields that name a recurring time. The fields are minute, hour, day of month, month, and day of week. The expression `0 2 * * *` means 'minute zero of hour two of every day of every month, regardless of weekday', which is 2am every night. Cron expressions are dense and easy to misread; production teams paste them through valida

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