Automatically delete expired WooCommerce Transients in WordPress

Transients are used to store information into the WordPress database with an expiration time, the server load does not increase, and in most scenarios, it helps to speed the site.

However if your WordPress database options table (wp_options) accumulates old, expired transients that didn't get automatically cleared, they could end up bloating your database and even slowing down your website.

WooCommerce has a tool that allows you to the Products' Transient Cache and all the expired transients from WordPress. You can access it under WooCommerce > System Status > Tools

However if you need to delete the expired WooCommerce Transients (or any other Transients for that matter) in an automated manner, you have to implement some kind of Cron Job. Cron is a time-based job scheduler that allows you to run repetitive tasks unattended.

A "real" Cron Job always runs on the (Linux) server side, and generally speaking if you have access to the server tools needed to set it up, is always a much preferred solution. A WordPress Cron on the other hand is rather a pseudo-cron system, that is limited by several conditions. If you would like to dive into the technicalities here is an article that explains the differences in detail:
http://www.smashingmagazine.com/2013/10/16/schedule-events-using-wordpress-cron/

Since in most cases you will not have access to those server tools, you can place the following snippet into your functions.php file and then visit your site to force it to run:
 global $wpdb; $sql = 'DELETE FROM ' . $wpdb->options . ' WHERE option_name LIKE "_transient_%"'; $wpdb->query($sql);

I was about to modify such script to purge expired transients on a daily basis for a WooCommerce installation, but it turns out someone has already come out with a solution, the 'Delete Expired Transients' plugin. I checked its code and it seems to be well-written and optimized for performance, using few resources. You can get it here:
https://wordpress.org/plugins/delete-expired-transients/

After you install and activate the plugin, the first thing it does is to schedule a housekeeping task to delete expired transients. This means that there may not be any transients found when you visit its settings page under the tools menu right after installing the plugin, because they may have already been deleted.

That means that you'll probably never need to delete expired transients manually, because they'll be automatically deleted on a daily basis, which should be more than enough to keep the database uncluttered under any situation.