Object caching stores the results of expensive database queries temporarily, so WordPress doesn’t have to run the same query repeatedly for every visitor who requests similar data.
It’s a more advanced layer of caching compared to page caching, working at the database and application level rather than caching entire finished pages.
Persistent vs Non-Persistent Object Cache
WordPress includes a basic, non-persistent object cache by default, which only lasts for a single page load and then clears itself. A persistent object cache, often powered by tools like Redis or Memcached, keeps that cached data available across multiple visits, offering a much bigger performance boost on busy sites.
When It’s Worth Setting Up
Object caching tends to matter most for larger, database-heavy sites — think online stores or membership platforms with lots of dynamic content. A small blog with light traffic usually won’t notice much difference from adding it.
Many managed WordPress hosting providers offer persistent object caching built into their plans, since it requires server-level configuration beyond what a typical plugin alone can set up.