Architecture Decision Record (ADR) Template for Engineering Teams
Every engineering team makes dozens of architecture decisions each quarter. Six months later, no one remembers why the database was chosen, why the API was structured that way, or what alternatives were considered. The result is teams relitigating the same decisions or, worse, reversing good decisions because the original context was lost.
Architecture Decision Records solve this problem. An ADR is a short document that captures a single architecture decision along with its context, the alternatives considered, and the expected consequences. After implementing ADRs across four engineering organizations over 22 years, I consider them the highest-leverage documentation practice a tech lead can adopt.
Why ADRs Are Worth the Effort
Writing an ADR takes 20 to 30 minutes. That small investment pays off in three specific ways:
- Onboarding speed. New team members can read the ADR log and understand not just what the system looks like, but why it looks that way. This cuts ramp-up time significantly.
- Decision quality. The act of writing down the context and alternatives forces you to think more rigorously. I have changed my mind during the writing process more times than I can count.
- Reduced re-litigation. When someone asks "why didn't we use Kafka?", you can point to the ADR where you evaluated it and explain the reasoning. This saves hours of circular discussion.
The goal of an ADR is not to justify a decision. It is to capture the context so that future teams can make better decisions with better information.
How to Use This Template
Store ADRs alongside your code in a docs/adr/ directory. Number them sequentially. Use markdown for easy reading in pull requests. Each ADR should be a standalone document that makes sense without reading any other ADR, though you can reference related ones.
Not every decision needs an ADR. Use them for decisions that are hard to reverse, affect multiple teams, or involve significant tradeoffs. A good rule of thumb: if the decision will still matter in six months, write an ADR.
ARCHITECTURE DECISION RECORD TEMPLATE
ADR-[NUMBER]: [Short Title of Decision]
Status: [Proposed | Accepted | Deprecated | Superseded by ADR-XXX]
Date: [YYYY-MM-DD]
Decision Makers: [Names and roles of people involved]
Context
[Describe the situation that requires a decision. What is the problem? What constraints exist? What forces are at play? Include business context, technical constraints, team capabilities, and timeline pressures. This section should be understandable by someone who joins the team six months from now.]
Decision
[State the decision clearly and concisely. Use active voice: "We will use PostgreSQL as the primary datastore for the payments service." One to three sentences.]
Alternatives Considered
- [Alternative A]: [Brief description, 1-2 sentences]. Pros: [list]. Cons: [list]. Why rejected: [reason].
- [Alternative B]: [Brief description]. Pros: [list]. Cons: [list]. Why rejected: [reason].
- [Alternative C]: [Brief description]. Pros: [list]. Cons: [list]. Why rejected: [reason].
Consequences
Positive:
- [Expected benefit 1]
- [Expected benefit 2]
Negative:
- [Known tradeoff or risk 1]
- [Known tradeoff or risk 2]
Neutral:
- [Side effects that are neither clearly positive nor negative]
Implementation Notes
[Optional: any tactical details about how the decision will be implemented, migration steps, or timeline. Keep brief.]
Related Decisions
- [ADR-XXX: Related decision title]
Example: Filled-In ADR
ADR-007: Use Event Sourcing for Order Processing
Status: Accepted
Date: 2025-02-15
Decision Makers: Fernando (Tech Lead), Sarah (Staff Engineer), Mike (Backend Lead)
Context
Our order processing system needs to support audit trails, order state reconstruction, and eventual integration with the analytics pipeline. The current CRUD-based approach loses intermediate states and makes debugging customer issues difficult. We process approximately 50,000 orders per day with 15% growth month-over-month.
Decision
We will adopt event sourcing for the order processing domain using our existing PostgreSQL database as the event store, with materialized views for read queries.
Alternatives Considered
- CRUD with audit log table: Simpler to implement. Pros: team familiarity, lower learning curve. Cons: audit log can diverge from actual state, does not support state reconstruction. Why rejected: does not solve the debugging problem.
- Event sourcing with Kafka: Industry standard for event-driven architectures. Pros: built-in partitioning, replay capability. Cons: operational overhead, team has no Kafka experience, adds infrastructure cost. Why rejected: operational complexity not justified at our scale.
Consequences
Positive:
- Complete audit trail for every order state change
- Ability to reconstruct order state at any point in time for debugging
Negative:
- Team needs to learn event sourcing patterns (estimated 2-week ramp-up)
- Read queries are more complex due to materialized views
Tips for Writing Effective ADRs
- Keep them short. If an ADR exceeds two pages, you are including too much detail. Save implementation specifics for design docs.
- Write the context section for a stranger. The most common failure mode is assuming the reader shares your current knowledge. They will not.
- Include rejected alternatives. This is the most valuable part of an ADR. It prevents future teams from re-evaluating options you already considered.
- Review ADRs in pull requests. Treat them as code. Get feedback from stakeholders before accepting.
- Never delete ADRs. Mark them as deprecated or superseded instead. The history matters. For more on documentation practices, see our documentation guide.
Learn to Make Better Technical Decisions
The First Lead course covers decision-making frameworks, technical leadership, and the business context that shapes architecture choices. Built from 22 years of experience across startups and scale-ups.
Enroll in First Lead