Scheduled Actions

Great question, I would have asked the same thing.

First of all, Action Scheduler is a scalable, traceable job queue for background processing large queues of tasks in WordPress. It is designed for distribution in WordPress plugins.

Action Scheduler is built by Woocommerce, and used by many plugins, including Woocommerce, WP Forms, WP Activity Log, All In One SEO, etc.

In comparison to WP Cron (which is the built-in WordPress job queue), Action Scheduler is much more reliable and has much better performance.

Site Reviews uses Action Scheduler to:

1. Automatically run plugin migrations (if needed) after the plugin is updated, without blocking and/or potentially aborting the update process due to server timeout settings.
    
2. Send email notifications when reviews are submitted. Using Action Scheduler allows notifications to gracefully fail if the server is not configured correctly for sending mail. In some previous situations, this was causing the review submission to abort.
    
3. The Review Notifications add-on depends on Action Scheduler to reliably schedule the sending of custom notifications.
    
4. Hosting providers with lower resources commonly disable WP Cron to reduce the resources consumed websites, and “optimisation” plugins sometimes disable WP Cron for the same reason. Using Action Scheduler allows Site Reviews to prevent this issue from breaking functionality.

If your reason for not liking Action Scheduler is because it creates custom tables in your database to handle the job queues, then it may not be the best reason. Adding additional database tables will generally not slow down your website (particularly if your database uses the InnoDB engine), and it allows for higher performant SQL queries which is better for your website than cluttering up the wp_posts, wp_postmeta or wp_options tables for example. The wp_options table should be lean, and the wp_posts/wp_postmeta table combination is notoriously slow due to the way it is indexed and structured.

Additionally, Site Reviews uses custom database tables to store review details and manage the review assignments, this allows it to perform incredibly fast SQL queries and to easily manage tens of thousands of reviews with very little performance impact.

If Site Reviews did not use Action Scheduler, it would likely have needed to add additional database tables regardless. Since Site Reviews does use Action Scheduler, the database tables that are created by Action Scheduler are shared by any other plugin which also uses it.

Action Scheduler is actively used on tens of thousands of production sites already. In fact, every month, Action Scheduler processes millions of payments as part of the WooCommerce Subscriptions extension. In other words, it’s a robust solution (better than WP Cron) for queuing background tasks, and it does the job well and efficiently.