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Design

ADR

An Architecture Decision Record is a short document that captures a single architecture choice — what was decided, why, what alternatives were rejected, and what consequences the team accepts. ADRs are immutable: a new decision creates a new ADR that supersedes the old one. They live in the codebase or design tool so the rationale travels with the architecture.

ADRs typically follow a four-section structure: context (the problem), decision (what was chosen), consequences (what this commits the team to), and status (proposed / accepted / superseded). A team's ADR log is its institutional memory; without it, every architecture question gets re-litigated when a new engineer joins. The format was popularised by Michael Nygard's 2011 blog post and has become canonical for medium-to-large engineering organisations.

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