Using ADRs to Record Design Decisions

Using ADRs to Record Design Decisions

In software development, the journey from idea to implementation is filled with pivotal decisions. These decisions, whether about architectural patterns, technology stacks, or specific design trade-offs, shape the direction and quality of a software product. Yet, without a proper mechanism to document these choices, teams risk losing critical context, repeating past mistakes, or failing to justify their paths to stakeholders. Architectural Decision Records (ADRs) offer a lightweight and effective solution for capturing and communicating design decisions throughout the development lifecycle.

What Are Architectural Decision Records (ADRs)?

Architectural Decision Records (ADRs) are concise documents that capture key architectural or design decisions made during a project. Initially proposed by Michael Nygard, ADRs are structured to include the context, decision, and consequences associated with a specific issue or solution. They serve as a chronicle of why certain decisions were made and what alternatives were considered, helping current and future team members understand the system’s evolution.

Unlike traditional documentation, which can be lengthy and unfocused, ADRs are intentionally brief and follow a consistent format, typically including:

• Title – A clear and descriptive heading

• Context – Background information about the issue or problem

• Decision – The resolution or choice made

• Status – The current state (proposed, accepted, deprecated, etc.)

• Consequences – The impact of the decision, including trade-offs

• Alternatives Considered – Other options evaluated before settling on the decision

This standardized structure ensures that ADRs are easily readable and maintainable, even as projects grow in complexity.

Why Use ADRs?

1. Traceability
   ADRs create a timeline of decision-making that enables developers to trace the rationale behind a particular design. This is especially useful during onboarding, audits, or retrospectives, providing insight into how and why the system reached its current state.

2. Team Communication
   By documenting decisions in ADRs, team members—especially those joining later—gain access to the same historical context. This reduces misunderstandings, aligns everyone on the project vision, and minimizes repeated discussions over previously settled matters.

3. Knowledge Preservation
   In fast-moving teams or environments with high turnover, institutional knowledge can easily be lost. ADRs help preserve this knowledge in an accessible format, ensuring continuity even when key individuals leave the project.

4. Facilitating Decision-Making
   The very act of writing ADRs encourages thoughtful decision-making. When developers are required to explicitly state the context and consequences of a choice, they tend to make more deliberate and rational decisions.

5. Support for Change Management
   Systems evolve. ADRs help teams reassess past decisions in light of new requirements or constraints. Deprecated or superseded ADRs form a natural audit trail, making it easier to revisit and revise outdated architectural choices.

When to Write an ADR

An ADR should be created when a design decision has a significant impact on the software’s architecture, performance, scalability, or maintainability. Examples include:

• Choosing a database technology

• Deciding on a microservices vs. monolithic architecture

• Selecting a programming language or framework

• Defining deployment strategies

• Establishing coding conventions or design patterns

Not every small decision requires an ADR. Focus on those that are difficult to reverse, have long-term implications, or involve considerable trade-offs.

How to Write Effective ADRs

1. Be Concise and Clear
   Avoid verbosity. ADRs should communicate the essential points clearly. Use simple language that can be understood even by those not involved in the original decision.

2. Use a Consistent Template
   Adopt a standard ADR format across the team. This consistency ensures readability and makes it easier to browse through multiple ADRs.

3. Version Control Integration
   Store ADRs in version control systems like Git alongside the source code. This way, they evolve with the codebase, and changes can be reviewed and discussed through pull requests or merge reviews.

4. Number and Link ADRs
   Numbering ADRs and linking related decisions helps build a decision graph. This is particularly useful when decisions are revisited or superseded by new ones.

5. Keep ADRs Alive
   Like code, ADRs should not be static. If a decision becomes obsolete or is reversed, mark the ADR as deprecated and create a new one that reflects the updated direction. Maintain an index file to track the status and relevance of all ADRs.

Tools and Practices Supporting ADRs

While ADRs can be written in plain text using markdown, several tools and practices can streamline their adoption:

• ADR Tools: Tools like adr-tools help automate the creation and management of ADRs using command-line interfaces.

• Templates: Establishing an internal template with your preferred structure promotes uniformity.

• Integration with CI/CD: Include ADR checks in your CI/CD pipeline to ensure that architectural changes are documented before merging.

• Team Norms: Establish team-wide agreements about what decisions require ADRs and who is responsible for creating and reviewing them.

ADRs in Agile Environments

One common misconception is that Agile teams, due to their iterative and fast-paced nature, do not need detailed documentation. However, Agile does not mean undocumented. It values working software over comprehensive documentation, not no documentation. ADRs strike the perfect balance—they’re light enough to avoid bureaucracy but structured enough to provide lasting value.

ADRs align well with Agile ceremonies:

• During sprint planning, teams can draft or propose new ADRs for upcoming technical challenges.

• In retrospectives, ADRs can be reviewed to evaluate whether past decisions still hold or need updates.

• During backlog grooming, ADRs can help guide technical refinement and decision validation.

Case Study: ADRs in a Microservices Migration

Consider a software team transitioning from a monolith to microservices. Early decisions include defining service boundaries, selecting a service mesh, and choosing a communication protocol (REST vs. gRPC).

By creating ADRs for each decision:

• The team ensures alignment on service granularity and responsibilities.

• New developers understand the rationale behind tool selections without lengthy explanations.

• Decisions can be revisited as the system matures, with clear records of what has changed and why.

In such scenarios, ADRs become invaluable in managing complexity and maintaining architectural integrity over time.

Common Challenges and How to Overcome Them

1. Neglecting to Update ADRs
   Solutions: Incorporate ADR updates into the development workflow. Assign responsibility during sprint reviews or code merges.

2. Inconsistent Use Across Teams
   Solutions: Include ADR practices in onboarding and development guidelines. Promote success stories from teams effectively using ADRs.

3. Overproduction of Low-Impact ADRs
   Solutions: Establish criteria for what decisions warrant ADRs. Focus on impactful, architectural-level decisions.

4. Resistance to Documentation
   Solutions: Highlight ADRs as tools for clarity and efficiency. Demonstrate how they reduce rework and improve team autonomy.

Conclusion

Architectural Decision Records are a lightweight yet powerful way to capture the history of a system’s evolution. By documenting context-rich decisions and their justifications, ADRs empower teams with clarity, continuity, and collaboration. They offer a scalable practice for modern development environments where change is constant, and decisions shape the long-term health of software systems. Whether working on greenfield projects or maintaining legacy systems, integrating ADRs into your workflow ensures that your design decisions are never lost in time.