Cron jobs

A cron schedule has five fields: minute, hour, day of month, month and day of week. So '0 2 * * *' means 2 a.m. every day and '*/15 * * * *' means every fifteen minutes. On a server, the cron program reads these lines from a crontab file and runs each command at the matching times.

Serverless apps have no always-on machine, so hosts offer their own versions: Vercel Cron Jobs, Cloudflare Cron Triggers, GitHub Actions schedules, pg_cron inside PostgreSQL and QStash schedules. Most run in UTC, may start a little late and can overlap a previous run that has not finished, so jobs should be safe to run twice.