[robomc]

Code as documentation only works if all your infrastructure is managed programatically, there are good tests, the code is good, and overall complexity is low.

I mean, if your downstream partner calls up to say that the custom analytics feed from your xyz service is returning null data, but not erroring, and the guy that implemented that feed (with rolled eyes, thinking it was an inelegant hacky concession to a noisy customer) left in 2015, where do you even start? How much code from how many codebases and configuration management repos are you going to have to read through just to work out what kind of problem you've got?

Some type of high level documentation - what services / products exist, what infrastructure does each use, how is each one managed and tested, what is worrisome about it or what has tended to go wrong in the past - is going to help a lot.