Cloud Architecture Decisions Worth Documenting

Architecture documentation is most useful when it explains decisions. Diagrams show structure, but decisions explain why the structure exists and when it should change.

For cloud systems, documentation should capture constraints, assumptions, data flow, ownership, security boundaries, and failure behavior. Future engineers rarely need every meeting note. They need the reasoning that prevents accidental rewrites.

Document the tradeoffs

• Why this managed service was chosen.
• What failure modes are acceptable.
• Which costs were optimized and which were intentionally ignored.
• What would cause the design to be reconsidered.

Good documentation helps a team operate the system with context, not folklore.