Every time WordPress builds a page it asks the database dozens of questions. What is this site called, what are the menu items, which plugins are active, what does this option say. The answers rarely change, but the database gets asked every single time.
The Redis object cache remembers those answers in memory, so the second visitor gets them instantly instead of the database doing the work again.
What it improves
- Admin speed. The WordPress admin cannot be page-cached, because every page is different for a logged-in user. The object cache is what makes the admin feel quick.
- Logged-in visitors. Anyone with a cart or an account skips the page cache. The object cache still helps them.
- WooCommerce. Product pages, cart pages and checkout are all database-heavy. This is where the object cache earns its keep.
- Any site with a lot of plugins, because each one adds database queries.
Do I need to install anything?
No. It is set up for you, on every plan, including Starter. If you install a plugin that offers to manage an object cache, you do not need it.
When to clear it
Almost never. It looks after itself. Clear it if:
- You have changed a setting and the site is still showing the old value
- You have just finished a large import or migration
- Something looks stale that a page-cache clear did not fix
Clear it from the site's page in your panel. Clearing it is safe. The cache rebuilds itself in seconds. It never contains anything you cannot afford to lose.
What it does not do
It is not a page cache and it will not make an inefficient plugin efficient. If one plugin is running a thousand queries per page, caching the answers helps, but removing the plugin helps more.
Non-WordPress sites
Laravel, Django, Node.js and other apps can use it too. The connection details are in your panel.
The assistant in your control panel can see your actual account and answer about your sites, your plan and your usage. For anything else, email [email protected] and a person will answer.