Describes the guidelines for how a system should be constructed. Instead of a hard rule, like the architecture decisions, the guidelines are intended to “guide”.
Design (instead of architecture) is more in the “implementation details”, in the code base (e.g. design patterns), or the actual used technology. Architecture is the structure where the design lives in. Note that the line can be grey sometimes.
Example: “Wherever possible, leverage async communication for decoupling”
