Page cache vs object cache in WordPress: which one do you need

When a WordPress site is slow, the first recommendation is usually "install a caching plugin." The problem is that "cache" covers very different layers, and mixing them up leads to configuring what you don't need and leaving unresolved what you do. Here's a practical guide to distinguish page cache from object cache.

What object cache does

WordPress queries the database many times per request: options, metadata, terms, users. Object cache (with backends like Redis or Memcached) stores the results of those queries in memory so they aren't repeated.

• It reduces the load on the database.
• It helps both anonymous visitors and logged-in users.
• But PHP still runs: WordPress boots, loads plugins and the theme, and builds the page on every visit.

It's very useful in dynamic areas: the admin panel, a store with a cart, a membership site.

What page cache does

Page cache stores the finished HTML of each URL. When a visitor arrives, they are served that result without rebuilding it. Depending on how it's implemented, it can completely avoid going through PHP and the database.

Static HTML as a file

The most direct variant is writing the HTML as a file and letting the web server serve it. There's no WordPress boot or queries: it's the same as serving an image. In how cache.lat works we explain the process of generating and regenerating those files, and in the technical data you'll find the implementation details.

One or the other? It depends on who visits

• Blog, corporate site, landing pages, documentation: almost all traffic is anonymous and content changes little. Page cache has the biggest impact.
• Online store: catalog pages can be cached, but cart, checkout, and customer account must stay out. Here object cache contributes quite a bit.
• Sites with massive login (courses, communities): page cache helps little; object cache and good hosting matter more.

Common mistakes

1. Stacking three caching plugins. They step on each other and generate hard-to-debug behaviors. One page layer and, if needed, one object layer.
2. Not excluding dynamic content. Cart, checkout, forms with nonces, and private areas should not be served from a shared copy.
3. Forgetting invalidation. If you publish or edit a post and the visitor still sees the old version, the cache isn't regenerating as it should.
4. Measuring only with the site "warm." Also test the first visit after clearing the cache to know how much it really costs to build each page.

How to decide in three steps

1. Check what percentage of your traffic is anonymous. If it's the majority, start with page cache.
2. Identify the URLs that should never be cached and exclude them explicitly.
3. If after that the panel or logged-in areas are still slow, add object cache and review heavy queries and plugins.

How to measure the effect

There's no need to invent numbers: compare the time to first byte (TTFB) of a URL before and after, from the same location and several times. With a well-applied page cache, the difference for anonymous visitors is usually evident in that metric, and that has an impact on metrics like LCP.

Next step

If you want to see how cache.lat fits into your site, the documentation walks through installation and exclusions, and you can check the product page. And if you have a particular case, write to us from contact.