Glossary Terms

page caching

Page caching saves the fully built HTML of a page after the first visitor loads it, then serves that ready-made copy to everyone after, skipping the PHP and database work each time. Without it, every single request runs PHP, hits the database, and renders templates, which can take anywhere from half a second to a couple of seconds on a busy shared server; with it, the saved file goes out in under 50 milliseconds. It's different from object caching, which stores individual query results, and fragment caching, which stores parts of a page. Most managed hosts build it in (WP Engine calls theirs EverCache), and the genuinely tricky part is invalidation: clearing the cached copy at the right moment when content changes.