Design Docs at Google

Design docs at Google are informal documents that are used to define software designs. They serve the purpose of early identification of design issues, achieving consensus, ensuring consideration of cross-cutting concerns, scaling knowledge, forming an organizational memory, and acting as a summary artifact. Design docs should include a context and scope section, list out the goals and non-goals, provide the actual design with details, discuss alternatives considered, address cross-cutting concerns, and be of a sufficient detail but also short enough to be read by busy people. They should be written when the solution to the design problem is ambiguous and there is a need for organizational consensus, involvement of senior engineers, consideration of cross-cutting concerns, and documentation of legacy systems.