As an extension developer, I often ran into issues where my code would not be executed / updated due to some cache hit in earlier parts of the code. Documentation is spread out all over MediaWiki, and incomplete.
Who would benefit
Extension developers who write code that dynamically changes page content and need to know when and how to invalidate the caches.
A good starting point is https://www.mediawiki.org/wiki/Manual:Caching. We need to complete the information missing for some cache types. A rough description of which caches are used when in the execution order would be extremely helpful (maybe in relation to some central hooks). Also, some information of how these caches can be invalidated within the code and in general should be added.