Cron (scheduled tasks)
A cron is a system task executed automatically at intervals defined by a cron expression ('0 2 * * *' = every day at 2 AM). In web environments, it triggers recurring processes: sitemap generation, email sending, cache clearing, and data synchronization.
In practice
The five-field cron expression (minute hour day month weekday) is universal on Linux. In cloud or serverless environments, managed alternatives replace the system crontab: Vercel Cron Jobs, GitHub Actions schedules, Supabase Edge Functions cron. A common mistake is scheduling a heavy cron job (generating 10,000 pages) during peak traffic hours — scheduling intensive tasks between 2 AM and 5 AM reduces impact on availability.