I like Arc42. It is aimed at documenting technical architectural decisions, the whys and constraints (budgetary et c) that lead to a particular design. It also

I like Arc42. It is aimed at documenting technical architectural decisions, the whys and constraints (budgetary et c) that lead to a particular design. It also outlines the main boundaries, the key interactions. Architecture should not be about the details. Rather it should be like a guide so that the developer can look at the source and see for themselves.