Documenting Architecture Decisions

Documenting Architecture Decisions

Core principle

Record why an architecturally significant choice was made while the context is still available. An ADR is a decision record, not a design essay and not retrospective justification.

When a decision deserves an ADR

Capture a decision when changing it later would be costly or when it materially affects:

• system structure or deployment shape;
• reliability, security, performance, availability, or other quality attributes;
• dependency and ownership boundaries;
• published interfaces or data contracts;
• frameworks, persistence, messaging, infrastructure, or other construction techniques;
• a recurring technical debate that needs one shared source of rationale.

Do not create ADRs for routine implementation details that are cheap to reverse and already obvious from the code.

Minimal record

Keep each ADR focused on one decision and include:

1. Title and status — proposed, accepted, rejected, or superseded.
2. Context — the problem, constraints, forces, and evidence that make a decision necessary.
3. Decision drivers — the quality attributes or business/engineering outcomes that matter most.
4. Considered options — realistic alternatives, including keeping the current state when relevant.
5. Decision — the selected option in direct language.
6. Consequences — benefits, costs, new risks, operational burden, and follow-up work.
7. Validation/review trigger — evidence that should confirm the decision and conditions that should cause it to be reconsidered.

Lifecycle

Discuss the ADR while it is proposed. Once accepted, preserve it as historical context. If later evidence changes the decision, create a new ADR that supersedes the old one rather than rewriting history.

Link implementation changes to the relevant ADR when that connection helps reviewers evaluate architectural consistency.

Quality checks

A useful ADR lets a future engineer answer:

• What problem were we solving?
• Which constraints and trade-offs mattered?
• What alternatives were actually considered?
• Why did this option win then?
• What complexity did we knowingly accept?
• What would make us revisit the choice?

If the record only names a technology and says it is “best”, the decision is not sufficiently documented.

Reference

• AWS Prescriptive Guidance, architectural decision record process: https://docs.aws.amazon.com/prescriptive-guidance/latest/architectural-decision-records/adr-process.html