WordPress Query Cache

WordPress 6.9 changed how query cache groups store invalidation state. Core now uses stable cache keys with stored salts instead of baking changing last_changed values into every key. This reduces unreachable cache keys on high-update sites.

This skill is for plugin code that directly reads/writes object-cache entries for query results. Most plugins should not do that.

Do not trigger this skill merely because code uses a transient or has a slow query. Use wp-database-performance-audit for general SQL shape, indexes, pagination, N+1 calls, payload size, or cache stampedes.

When to use this skill

Trigger when ANY of the following is true:

• Code directly calls wp_cache_get() / wp_cache_set() in query groups such as post-queries, term-queries, user-queries, comment-queries, site-queries, or network-queries.
• Code builds cache keys with wp_cache_get_last_changed().
• The task mentions persistent object cache misses, query cache bloat, cache invalidation, or stale query results after updates.
• A plugin duplicates WP_Query, WP_User_Query, WP_Term_Query, or WP_Comment_Query cache behavior.