Architecture Decision Records
Comprehensive patterns for creating, maintaining, and managing Architecture Decision Records (ADRs) that capture the context and rationale behind significant technical decisions.
When to Use This Skill
- Making significant architectural decisions
- Documenting technology choices
- Recording design trade-offs
- Onboarding new team members
- Reviewing historical decisions
- Establishing decision-making processes
Core Concepts
1. What is an ADR?
An Architecture Decision Record captures:
- Context: Why we needed to make a decision
- Decision: What we decided
- Consequences: What happens as a result
2. When to Write an ADR
| Write ADR | Skip ADR |
|---|
| New framework adoption | Minor version upgrades |
| Database technology choice | Bug fixes |
| API design patterns | Implementation details |
| Security architecture | Routine maintenance |
| Integration patterns | Configuration changes |
3. ADR Lifecycle
Proposed → Accepted → Deprecated → Superseded
↓
Rejected
Before drafting a standard, lightweight, or Y-statement ADR, read decision templates.
Before drafting a deprecation ADR or RFC, read deprecation and RFC templates.
ADR Management
Directory Structure
docs/
├── adr/
│ ├── README.md # Index and guidelines
│ ├── template.md # Team's ADR template
│ ├── 0001-use-postgresql.md
│ ├── 0002-caching-strategy.md
│ ├── 0003-mongodb-user-profiles.md # [DEPRECATED]
│ └── 0020-deprecate-mongodb.md # Supersedes 0003
ADR Index (README.md)
# Architecture Decision Records
This directory contains Architecture Decision Records (ADRs) for [Project Name].
## Index
| ADR | Title | Status | Date |
| ------------------------------------- | ---------------------------------- | ---------- | ---------- |
| [0001](0001-use-postgresql.md) | Use PostgreSQL as Primary Database | Accepted | 2024-01-10 |
| [0002](0002-caching-strategy.md) | Caching Strategy with Redis | Accepted | 2024-01-12 |
| [0003](0003-mongodb-user-profiles.md) | MongoDB for User Profiles | Deprecated | 2023-06-15 |
| [0020](0020-deprecate-mongodb.md) | Deprecate MongoDB | Accepted | 2024-01-15 |
## Creating a New ADR
1. Copy `template.md` to `NNNN-title-with-dashes.md`
2. Fill in the template
3. Submit PR for review
4. Update this index after approval
## ADR Status
- **Proposed**: Under discussion
- **Accepted**: Decision made, implementing
- **Deprecated**: No longer relevant
- **Superseded**: Replaced by another ADR
- **Rejected**: Considered but not adopted
Automation (adr-tools)
# Install adr-tools
brew install adr-tools
# Initialize ADR directory
adr init docs/adr
# Create new ADR
adr new "Use PostgreSQL as Primary Database"
# Supersede an ADR
adr new -s 3 "Deprecate MongoDB in Favor of PostgreSQL"
# Generate table of contents (to a separate file, so the hand-written
# index and guidelines in README.md are not overwritten)
adr generate toc > docs/adr/toc.md
# Link related ADRs
adr link 2 "Complements" 1 "Is complemented by"
Review Process
## ADR Review Checklist
### Before Submission
- [ ] Context clearly explains the problem
- [ ] All viable options considered
- [ ] Pros/cons balanced and honest
- [ ] Consequences (positive and negative) documented
- [ ] Related ADRs linked
### During Review
- [ ] At least 2 senior engineers reviewed
- [ ] Affected teams consulted
- [ ] Security implications considered
- [ ] Cost implications documented
- [ ] Reversibility assessed
### After Acceptance
- [ ] ADR index updated
- [ ] Team notified
- [ ] Implementation tickets created
- [ ] Related documentation updated
Best Practices
Do's
- Write ADRs early - Before implementation starts
- Keep them short - 1-2 pages maximum
- Be honest about trade-offs - Include real cons
- Link related decisions - Build decision graph
- Update status - Deprecate when superseded
Don'ts
- Don't change accepted ADRs - Write new ones to supersede
- Don't skip context - Future readers need background
- Don't hide failures - Rejected decisions are valuable
- Don't be vague - Specific decisions, specific consequences
- Don't forget implementation - ADR without action is waste