What is Cron Jobs?
Cron jobs are scheduled tasks that run automatically at defined time intervals — every hour, every day at midnight, every Monday morning. They automate recurring work without manual intervention.
In plain English
A cron job is like setting a recurring alarm on your phone. You define when it fires and what to do when it does — check emails, take out the trash, send a report. The alarm runs whether you're awake or not, reliably, on schedule.
How it works
Cron expressions define the schedule using five fields: minute, hour, day-of-month, month, and day-of-week. For example, '0 9 * * 1' means 'every Monday at 9am.' A cron runner (the OS scheduler, or a managed service) invokes your job at the specified time. The job performs its work and exits.
Why it matters for AI-built apps
Many app features rely on scheduled work: sending digest emails, cleaning up expired sessions, syncing data from third-party APIs, or generating reports. AI-generated apps often leave these as manual processes or miss them entirely. Reliable cron jobs make your app feel polished and reduce operational burden.
Best practices
Design cron jobs to be idempotent — running them twice should not double-process data. Add monitoring and alerting so you know when a job fails silently. For long-running jobs, use a job queue instead of a cron so the job can be retried and tracked individually.
Frequently asked questions
What happens if a cron job takes longer than its interval?
By default, a new instance starts while the previous one is still running — which can cause race conditions or duplicate processing. Use locking (a distributed lock in Redis) to prevent overlapping runs.
What services can I use to run cron jobs in production?
Vercel Cron, Railway cron tasks, Render cron jobs, and Trigger.dev are all good managed options. For more control, use pg_cron inside PostgreSQL or a dedicated job scheduler like Inngest.
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