Cron At Minute 30 (Half Past Every Hour)
Schedule a cron job at minute 30 of every hour using 30 * * * *. Full field-by-field breakdown with practical examples and implementation tips.
Cron Expression
30 * * * *
Field Breakdown
| Field | Value | Meaning |
|---|---|---|
| Minute | 30 | At 30 |
| Hour | * | Every hour (0–23) |
| Day of Month | * | Every day of the month (1–31) |
| Month | * | Every month (1–12) |
| Day of Week | * | Every day of the week (Sun–Sat) |
Detailed Explanation
The cron expression 30 * * * * schedules a task to run once at the 30-minute mark of every hour, every day of the year.
Field-by-field breakdown:
30(Minute): At minute 30 only. The task fires exactly at the half-hour mark, such as 1:30, 2:30, 3:30, 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 half-hour mark of each hour. Running at minute 30 is a common strategy to avoid the "thundering herd" problem that occurs when many cron jobs are scheduled at minute 0. By offsetting your task to the half-hour, you reduce contention for shared resources like databases, APIs, and network bandwidth. This is particularly useful in environments with many scheduled jobs. The schedule provides the same hourly frequency as 0 * * * * but at a different offset. This expression is supported by standard cron on Linux/macOS, as well as cloud services like AWS CloudWatch, Google Cloud Scheduler, and GitHub Actions.
Use Case
Ideal for staggering hourly report generation to avoid overlapping with other top-of-hour jobs, reducing database load during peak scheduling times.
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at min 30
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