If you care about the speed of your site, Comet Cache is one of those plugins that you absolutely MUST have installed 🙂 Comet Cache takes a real-time snapshot (building a cache) of every Page, Post, Category, Link, etc. These snapshots are then stored (cached) intuitively, so they can be referenced later, in order to save all of that processing time that has been dragging your site down and costing you money.
The Comet Cache plugin uses configuration options that you select from the options panel. See: Comet Cache -› Options in your Dashboard. Once a file has been cached, Comet Cache uses advanced techniques that allow it to recognize when it should and should not serve a cached version of the file.
I use Comet Cache on the majority of my sites (some running older themes don’t play well) alongside Autoptimize, and the combination has granted very fast page load times with suitably fast themes e.g. GeneratePress.