Like many here, I keep it described in ansible and documentation inside a git repository.

But I feel like it's lacking. After a while you have so many ansible playbooks and roles that they cannot give you a birds-eye view anymore.

I think I would MUCH prefer to have some sort of HTML representation, where adding an instance/service starts by adding to that representation, and you could click on every link or node to show its golden image setup, ansible configuration, etc.

THAT, I could show to a newcomer and he'd get it.