What are WordPress transients?
Transients are a method of temporarily storing cached data in the WordPress database, identified by a name and set to expire after a specific time. This helps enhance WordPress performance, speed up your website, and reduce overall server load. As of WordPress version 4.9, transients housekeeping is managed by the WordPress core, so manual cleanup is generally unnecessary unless you have specific needs.
There are three types of transients:
Expired transients: These have expired but still exist in the database and can be safely removed. You can use the Advanced Database Cleaner plugin to clean them.
Transients with an expiration: These are still valid and used by the core, plugins, or themes. They should not be cleaned unless you are certain it is safe to do so.
Transients with no expiration: These may still be valid but lack an expiration date. They also should not be cleaned unless necessary.