Agreed. This doesn’t sound like what I’m referring to: Caching database queries to Redis or Memcached to speed up large queries that don’t change often or the same query run on the same page multiple times. From my basic understanding, WP has a built-in way to expire the cached objects when they change, which allows support for dynamic content like membership sites. I haven’t dug into it, but I assume it’s just a matter of making sure plugins put in the actions to expire the cache for the specific query whenever something that would affect the operation of the plugin changes in the db. So then WP clears that cached object from Redis/Memcached (or, more specifically, probably allows the caching plugins to react via a hook), and the next time it needs to run the query it doesn’t find it in cache, so it goes to MySQL to grab it and caches the response. Of course, it’s probably way more complicated than this, but this is how I think of it without having actually tried to implement or research how to implement it as a plugin developer (which I’m not).