I have found Architecture Decision Records to be great for this. They capture why a decision was made and the context/options at the time. They also provide an

I have found Architecture Decision Records to be great for this. They capture why a decision was made and the context/options at the time. They also provide an immutable linear log of decisions which is nice for on boarding. https://github.com/joelparkerhenderson/architecture_decision_record https://github.com/joelparkerhenderson/architecture_decision...