[Navarr]

Edge Side Includes. Imagine putting some sort of template syntax in a file, that file is cached, and when it's called from cache it grabs a file from the remote server based on the template syntax.

[predakanga]

Notably, implementing ESI directly at Cloudflare's edge enables them to cache page fragments, rather than fully constructed pages.

That could do wonders both for the size of caches and for cache hit-rates