In a world of dependencies and online package management, documentation tools are designed and optimised around the question "how do I use your library?".

But for companies that build systems to do something, and not libraries, there is another critical question "how does the system work? how can I change it?"

Library-based documentation is inline with the code and under the same version control system.

All too often architectural documentation is outside the code and poorly kept in sync.

This talk will look at another way of thinking about documenting systems a way that keeps architectural docs in the github repo and which plays nice with ExDoc.