Object caching is a server-side caching strategy that stores the results of database queries and PHP computations in fast memory — typically Redis or Memcached — so identical requests can be served from memory rather than re-executing the database query. WordPress includes a built-in non-persistent object cache (the WP_Object_Cache class) that stores results within a single page request but discards everything at the end of that request. For persistent object caching that survives across page loads, a memory store must be connected via a wp-content/object-cache.php drop-in. Redis Object Cache by Till Krüss is the most widely used WordPress plugin for this. Managed WordPress hosts including WP Engine, Kinsta, and Pressable provide persistent Redis object caching by default. Object caching delivers the greatest benefit on sites with repeated expensive queries: WooCommerce product lookups, membership site permission checks, or news archives with complex tax queries — where reducing database calls from 50+ to 2–3 per page load is achievable.
Glossary entry