Architecture decisions get lost when someone leaves or a Slack thread scrolls away, and six months later the team re-litigates a choice that already had a good reason. Architecture Decision Records (ADRs) write that reason down as context, options, decision, and consequences, which matters most when requirements keep moving.
What an ADR contains
An ADR is a short document that captures one significant architectural decision with its context and consequences: the reasoning, the alternatives considered, and why the final choice won. The collection of ADRs for a project is its Architecture Decision Log (ADL), which is part of what the literature calls Architecture Knowledge Management (AKM).
What ADRs change on a team
Knowledge that survives turnover
The reasoning behind a decision stays with the codebase when the people who made it move on. New developers read the log instead of reconstructing history from commit messages, which shortens onboarding and keeps the team from repeating a mistake it already paid for.
Decisions everyone can read
A written decision is visible to every engineer and stakeholder, including the implications they might not have been in the room for. For technical leaders, that visibility is how a direction stays aligned without a meeting per question.
A record that keeps up with change
Agile teams change direction often, and an ADR is small enough to write at the moment a decision changes. A new ADR supersedes the old one instead of editing it, so the log shows both what the team decided and when it changed its mind.
Ownership of each decision
Each ADR states who made the decision and under what constraints. Knowing a decision will be written down and signed tends to produce a more careful discussion before it is made.
Less time re-arguing
When a past decision is one link away, an architectural discussion can start from the recorded tradeoffs instead of from zero, and the time goes back into implementation.
A way to learn how the team decides
For new and existing members alike, the log shows how the team weighs options, which is harder to learn from the code alone.
ADRs and stakeholder communication
ADRs also change how a team communicates with stakeholders outside engineering:
- Shared understanding: the decision, its context, and its implications are in one place, so stakeholders align on technical direction from the same text.
- Visible rationale: recording why a choice was made shows stakeholders that their input was weighed.
- Asynchronous reference: people read the decision on their own time instead of asking for the same explanation again.
- Engagement: inviting stakeholders to review an ADR brings them into the decision and makes buy-in more likely.
- Lower overhead: one source of truth replaces repeated conversations about past choices.
Templates and tools
The template I use
I recommend the MADR (Markdown Architectural Decision Records) template for capturing decisions in a consistent structure. MADR is lean, and although it started with architectural decisions, it now fits any significant decision.
- MADR template: https://adr.github.io/madr
- More ADR templates: https://github.com/joelparkerhenderson/architecture-decision-record
Tooling
Log4Brains is a CLI for creating and managing ADRs, and it generates a static site so the log is browsable.
- Log4Brains: Log4Brains GitHub Repository
Further reading
These are the sources I point teams to when they start an ADR log:
- ThoughtWorks Technology Radar: Adopt Lightweight ADRs
- Documenting Architecture Decisions by Michael Nygard: Nygard's Blog Post
- The GitHub ADR Organization: ADR GitHub Organization