Cron At Minute 0 (Top of Every Hour)

The cron expression 0 * * * * schedules a task to run once at the very start of every hour, every day of the year.

Field-by-field breakdown:

• 0 (Minute): At minute 0 only. The task fires exactly at the top of the hour, such as 1:00, 2:00, 3:00, and so on.
• * (Hour): Every hour from 0 through 23. No restriction on which hour the task runs.
• * (Day of Month): Every day from 1 through 31. No restriction on the day of the month.
• * (Month): Every month from January through December. No restriction on which month.
• * (Day of Week): Every day of the week from Sunday through Saturday. No restriction on the day of the week.

This means your task will execute 24 times per day, once at the start of each hour. This is one of the most commonly used cron schedules because it provides a clean, predictable cadence for periodic work without being too frequent. It is ideal for aggregation jobs, metric collection, or cache invalidation that should occur on a regular hourly basis. Since many systems use this same schedule, be aware of the "thundering herd" effect where many tasks start at minute 0 simultaneously. Consider adding a slight random delay if your task is resource-intensive. This expression is supported by standard cron on Linux/macOS, as well as cloud services like AWS CloudWatch, Google Cloud Scheduler, and GitHub Actions.