Architecture Decision Record (ADR) – Definition, Use Cases and Best Practices at a Glance
An Architecture Decision Record (ADR) documents an important architecture decision with context, considered alternatives, the decision, its rationale and consequences. ADRs keep technology decisions in software projects traceable over the long term.
Architecture Decision Record (ADR): Definition | Glossary
In long-lived software projects the most common question is not "How did we build this?" but "Why did we decide on this back then?". An Architecture Decision Record closes exactly this gap.
Instead of letting decisions disappear into people's heads, chat histories or meeting notes, an ADR records briefly and precisely which options were considered and why a particular one was chosen.
This saves a lot of time during team changes, vendor changes and modernisation – and prevents past decisions from being overturned without reason.
This glossary entry for Architecture Decision Record (ADR) gives you a clear Definition, practical Use Cases and Best Practices at a glance – with examples, pros and cons, and FAQs.
What is Architecture Decision Record (ADR)?
- Architecture Decision Record (ADR) – An Architecture Decision Record (ADR) documents an important architecture decision with context, considered alternatives, the decision, its rationale and consequences. ADRs keep technology decisions in software projects traceable over the long term.
An Architecture Decision Record (ADR) is a short, structured document that captures a single significant architecture decision.
A typical ADR contains the decision title, the status (proposed, accepted, superseded), the context and problem, the considered alternatives, the decision made with its rationale, and the resulting consequences – both positive and negative.
ADRs are usually versioned as simple Markdown files directly in the code repository and numbered chronologically, so the decision history of a system stays fully traceable.
Worth documenting are decisions with long-term impact: architecture style, database choice, cloud strategy, API approach, framework, security model, hosting or integration patterns. Deliberately not every small detail – ADRs should stay lean and avoid bureaucracy.
How does Architecture Decision Record (ADR) work?
As soon as a decision arises that shapes the system long term, a new ADR is created.
The team first describes the context and the problem to solve, then collects the seriously considered alternatives with their pros and cons, and finally records the decision made with its rationale.
The consequences are important: which new options arise, which constraints or technical debt are consciously accepted. The ADR is versioned together with the code in the repository.
If a decision later changes, the old ADR is not deleted but marked as "superseded" and linked to the new ADR – so the entire development line stays visible.
Practical Examples
A team chooses a relational database over a NoSQL solution and records in an ADR why consistency and reporting mattered more here than schema flexibility.
When choosing between REST and GraphQL, an ADR documents the decision for REST including the rationale around existing team know-how and caching requirements.
Before a cloud migration, an ADR records why a specific provider was chosen and which vendor lock-in risks are consciously accepted.
A new team member understands the key architecture decisions within hours by reading the ADRs, instead of building up implicit knowledge over months.
During a vendor change, the old team hands over a traceable decision history with the ADRs, so the new team does not overturn assumptions blindly.
Typical Use Cases
Long-term software projects with changing teams or vendors
Complex technology decisions with several serious alternatives
Legacy modernisation where earlier decisions must be understood
Choice of architecture style, database, cloud strategy or API approach
Security and integration decisions with far-reaching consequences
Audits and technical due diligence where decisions must be justified
Advantages and Disadvantages
Advantages
- Decisions stay traceable long term – even after team or vendor changes
- Low effort: short documents directly in the repository, no heavy tooling needed
- Prevents repeatedly reopening already-made decisions without a new reason
- Speeds up onboarding of new developers through a clear decision history
- Makes consciously accepted trade-offs and technical debt transparent
Disadvantages
- Requires discipline: ADRs must be maintained consistently and promptly
- Risk of over-documentation if trivial decisions are recorded too
- Outdated or contradictory ADRs cause confusion if the status is not maintained
- Provides no value if nobody reads the ADRs or considers them in reviews
- Does not replace overarching architecture documentation but complements it
Frequently Asked Questions about Architecture Decision Record (ADR)
What goes into an Architecture Decision Record?
An ADR contains the title and status of the decision, the context and problem, the considered alternatives, the decision made with its rationale, and the positive and negative consequences. Usually nothing more is needed – ADRs should be short and precise.
How does an ADR differ from architecture documentation?
Architecture documentation describes the current state of a system. An ADR documents a single decision with its rationale at a specific point in time. ADRs form the history that explains how today's architecture came to be.
Where are ADRs stored?
In practice, ADRs are usually numbered Markdown files in the same repository as the code, for example in a docs/adr folder. This keeps them versioned, searchable and closely tied to the state of the code.
Which decisions are worth documenting?
Decisions with long-term impact: architecture style, database, cloud strategy, API approach, key frameworks, security model, hosting or integration patterns. Trivial, easily reversible decisions do not belong in an ADR.
What happens when a decision changes?
The old ADR is not deleted but marked as "superseded" and linked to the new ADR. This keeps it traceable why an earlier decision was made and later revised.
Direct next steps
If you want to apply or evaluate Architecture Decision Record (ADR) in a real project, start with these transactional pages:
Architecture Decision Record (ADR) in the Context of Modern IT Projects
What this glossary entry gives you
This page gives a concise definition of Architecture Decision Record (ADR). You also get practical use cases and best practices at a glance.
You can use it to evaluate the technology for your next project. Architecture Decision Record (ADR) sits in the domain of Architecture. It plays a significant role across many IT projects.
Look beyond isolated technical merits
When you judge whether Architecture Decision Record (ADR) is the right fit, look beyond isolated technical merits. You should weigh the full project context.
Consider the following factors:
- Existing team expertise
- Current infrastructure
- Long-term maintainability
- Total cost of ownership (TCO)
Drawing on our experience from over 250 software projects, we have found that correctly positioning a technology or methodology within the broader project context often matters more than its isolated strengths.
How we help you decide
At Groenewold IT Solutions, we have worked with Architecture Decision Record (ADR) across multiple client engagements. We know its advantages and the typical challenges during adoption.
If you are unsure whether Architecture Decision Record (ADR) suits your requirements, ask us for an honest, no-obligation assessment. We analyze your situation. We recommend the approach that delivers the most value. We may suggest an alternative solution if that fits better.
Where to go next
For more terms in Architecture and related topics, open our IT Glossary.
For concrete applications, costs and processes, use our service pages and topic pages. There you will see many of the concepts from this entry applied in practice.
Related Terms
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