What Are Architecture Decision Records (ADRs)?
The most valuable knowledge in a software project is why a particular technology or approach was chosen. Architecture Decision Records (ADRs) are the standard method for documenting these decisions in a structured way.
What Is an ADR?
An ADR is a short, concise document that captures a single architectural decision. Each ADR typically includes:
- Title — Brief summary of the decision
- Status — Proposed, Accepted, Deprecated, Superseded
- Context — The circumstances under which the decision was made
- Decision — What was decided
- Consequences — Both positive and negative impacts
Why Should You Use ADRs?
1. Organizational Memory
When someone leaves the team, the reasoning behind architectural decisions leaves with them. ADRs make this knowledge permanent.
2. Fast Onboarding
A new developer joining the project can find answers to "why did we choose PostgreSQL?" or "why did we go with a monolith?" in minutes by reading ADRs.
3. Decision Traceability
When an architectural decision needs to be revised over time, knowing the original context is critical. ADRs provide that context.
4. Preventing Repetitive Debates
No more "we already discussed this." The decision is documented — anyone can read it.
How to Write an ADR
Basic Format
# ADR-001: Use PostgreSQL as Primary Database
## Status
Accepted (2026-01-15)
## Context
Our project has a relational data structure and
needs an ACID-compliant database. We also require
JSON support and full-text search capabilities.
## Decision
We will use PostgreSQL 16 as our primary database.
## Consequences
### Positive
- Strong ACID compliance
- Flexible data model with JSON/JSONB
- Row Level Security (RLS) for multi-tenancy
- Free and open source
### Negative
- Some operations easier in NoSQL will
require additional effort
- Horizontal scaling is more complex
than MongoDB
Characteristics of Good ADRs
- Short and concise — 1-2 pages is enough
- Context-focused — Not just what, but why
- Immutable — Old ADRs are never deleted, only superseded by new ones
- Numbered — Chronological ordering
ArchLog: A CLI Tool for ADRs
To simplify ADR creation, I built ArchLog. Here's what it offers:
Features
- 5 CLI commands — init, new, list, show, serve
- Markdown templates — Auto-generated ADR structure
- Web Viewer — Dark-themed visual interface
- Relation management — Links between ADRs
- Status workflow — Proposed → Accepted → Deprecated
Quick Start
npx archlog init
npx archlog new "Use PostgreSQL as Primary Database"
npx archlog serve
Three commands and your ADR system is ready.
Real-World Examples
BilgeOne Project
While developing the BilgeOne SaaS platform, we made dozens of architectural decisions:
- ADR-001: Choosing Next.js 14
- ADR-005: Multi-tenant architecture approach
- ADR-012: Supabase Row Level Security strategy
Every decision documented, every change traceable.
ADRs vs Other Documentation
| Method | Advantage | Disadvantage | |--------|-----------|--------------| | ADR | Structured, traceable | Requires discipline | | Wiki | Flexible, detailed | Quickly becomes outdated | | Confluence | Rich formatting | Poor searchability | | Code comments | Close to code | Can't see the big picture |
Conclusion
Writing ADRs has one of the highest return-on-effort ratios in software engineering. An ADR written in 10 minutes can prevent hours of team debate months later.
To learn ADR practices interactively, follow the Architect career path on LabLudus.