see “Caching Server” above. Varnish is an OpenSource product which is widely used for web applications.
A version control system is often used in programming environments but can also be used for other types of digital content. It’s like a backup system that keeps track of every single step that has been taken and while reviewing the programming code in a version control system, one can always go back in time to understand what has been done why, when and by whom. If something got broken, this also allows to roll back to an earlier stage that was known as working correctly.