Tech Due Diligence CQ-5: Code Documentation and Developer Onboarding

Start with a developer onboarding guide that takes someone from zero to productive. Cover development environment setup (ideally automated with a single command), codebase orientation, architecture overview with diagrams, your development workflow, key business domain concepts, and common debugging procedures. Keep architecture documentation lightweight but useful. At minimum, maintain a high-level system diagram showing major components and their interactions, data flow diagrams for critical user journeys, an infrastructure diagram of your deployment topology, and ADRs for significant technical decisions. Generate API documentation from code wherever possible. Tools like Swagger/OpenAPI for REST, GraphQL introspection, or Protocol Buffers definitions for gRPC keep docs in sync with the actual implementation automatically. Write operational runbooks for both routine and emergency procedures. Each one should cover when to use it, prerequisites, step-by-step instructions, expected outcomes, and what to do when things go sideways. Test runbooks periodically to make sure they still work. Make documentation a required part of your development process. Add it to PR checklists. Set the expectation that new features ship with documentation updates. Measure documentation quality practically: track new developer time-to-first-contribution, run periodic documentation reviews, check coverage of critical systems, and ask the team whether the docs are actually useful. Pick one documentation platform and stick with it. Stale, contradictory documentation scattered across multiple tools is worse than having no documentation at all.