The Power of the Paper Trail: Architecture Decision Records (ADRs)
Source: Dev.to
The ultimate output of knowledge work—software architecture and engineering—is decision making.
Regardless of the form it takes, recording the thought process behind key decisions is essential for:
- Maintaining clarity before, during, and after decisions are agreed upon.
- Preventing hindsight bias.
- Helping your future self and others understand the environment in which the decisions were made.
In this post I will share what I’ve been learning about Architecture Decision Records (ADRs) and their applications in software and data projects.
What are ADRs anyway?
Architecture Decision Records are essentially a paper trail for significant architectural decisions made during a project’s lifecycle. From now on I’ll refer to them simply as ADRs.
In my years as a software and data engineer I have rarely encountered ADRs. Documentation has taken many forms in the projects I’ve been part of: abandoned Notion pages, diagrams, sparsely detailed text files, or—sometimes—no documentation at all. When decisions change, ADRs help track those changes by introducing explicit states such as Proposed, Accepted, Rejected, and Superseded.
Why should you care?
Architectural decisions are among the most costly choices an organization makes. They affect:
- How easy it is to add new features.
- The system’s resilience and flexibility in the face of changing business requirements.
Interrogating and justifying these decisions with rigor—and doing so within the required time‑frame—becomes crucial. Moreover, the ADR framework can be adapted to many other fields and decision‑making processes.
How do you know what to document?
Not every decision warrants a paper trail; the administrative overhead would be a nightmare. Michael Nygard describes architecturally significant decisions as those affecting:
- Structure and construction techniques.
- Non‑functional characteristics (e.g., scalability, security).
- Dependencies and interfaces.
Ask yourself:
Is this decision reversible, and what is the cost of reversing it?
Olaf Zimmermann goes into great detail on this in his blog post about decision‑making criteria.
Lightweight ADRs: Setting Them Up
I’ll be the first to raise the issue of administrative overhead—gaining initial velocity on the habit of documentation is hard enough. Lightweight ADRs provide a format that delivers the benefits of documentation without dramatically affecting your workflow. There are even tools that help you manage ADRs, such as the adr-tools GitHub repo.
In my projects I simply add an /adr folder containing one Markdown document per decision, e.g.:
/adr
│ ADR 001 - Postgres for Operational Database.md
│ ADR 002 - Microservice Architecture for Orders Module.md
│ …I place diagrams directly in the folder and commit everything to source control, ensuring the documentation version‑matches the code. When a decision changes, I don’t edit the old ADR; I create a new one, mark the old one as Superseded, and link to the replacement.
The lifecycle of ADRs
The lifecycle of these documents varies with team dynamics and stakeholder responsibilities. There is always a primary contact (person or team) responsible for communicating, publishing, and maintaining the ADRs—i.e., moving an ADR from one state to the next.
Typical state diagram (adapted from the original source):
Proposed → Accepted → Superseded
↘
Rejected- Proposed – A new decision is drafted.
- Accepted – The decision is approved and becomes the current architecture.
- Rejected – The proposal is declined; the ADR remains for historical context.
- Superseded – A later ADR replaces this one; the old ADR is archived but still accessible.
By following this simple workflow, teams keep a clear, searchable history of why architectural choices were made—and how they evolved over time.
Happy documenting!
Conclusions
Documentation is a habit, and it’s especially important given the constantly changing landscape of tools and technologies that teams adopt. Although many organizational considerations that go into documentation frameworks haven’t been covered here, the rigor required to fill in and socialize ADRs alone should help stave off some of the pitfalls that come with insufficient documentation and decision silos.
Where ADRs live is just as important as writing them; it affects how they are versioned and maintained, which is, in my opinion, the biggest battle with technical documentation.