WordPress plugin: cron & background jobs

Scheduled work — daily cleanup, periodic API sync, deferred email send, retry on failed webhook delivery — is a normal part of plugin life. WordPress ships its own cron primitive (wp_schedule_event), and the WooCommerce-bundled Action Scheduler library extends the model into a proper queue. Picking between them and using the chosen one correctly is what this skill covers.

When to use this skill

Trigger when ANY of the following is true:

• Scheduling a periodic task (daily option cleanup, hourly token refresh, weekly digest email).
• Deferring work off the request thread (e.g. send email after the form submission returns).
• Debugging "my cron event was registered but never fires" or "fires multiple times" or "fires hours late".
• Deciding between native WP cron and Action Scheduler for a non-trivial background workload.
• Reviewing a plugin's activation / deactivation hooks for cron schedule + clear correctness.

Mental model — WP cron is pseudo-cron, not real cron

WordPress cron does NOT run on a system schedule. There is no cron daemon waking WP up. Instead: