Alright, I have changed the original plugin so that it caches only questions.
Each question gets updated when there is a change to it, such as answer added, edit, upvote etc.
It's beta, so please test it and report back: https://github.com/q2apro/q2apro-caching
You need to create a folder /qa-cache in your root. – The names of the cache files are the questionids!
The other versions of the plugin work well, however, they empty the entire file cache on incoming events. This plugin here only deletes the specific question page if it gets changed. So basically it should be more performant. Testers needed :)
Thanks for any feedback.