Write Architecture Decision Records that a future engineer can act on: a numbered, immutable record with the context that forced the decision, the options weighed with real trade-offs, the decision in one sentence, and the consequences including what becomes harder. Covers when a decision deserves an ADR, how to supersede one, and how to keep an index. Use when a design choice has cross-cutting or long-lived effects, when reviewers keep asking why, or when onboarding depends on decisions nobody wrote down.
