vinci rufus

Architecture Decision Records (ADRs)

2 minutes

As a veteran software architect with decades of experience designing large-scale systems, I’ve found that documenting architectural decisions is one of the most critical activities in a project. Complex systems that evolve over many years cannot be properly maintained without understanding the rationale behind key design choices. This is where Architecture Decision Records, or ADRs, come into play.

An ADR is a document that captures an important architectural decision made along with its context and consequences. For example, we might have an ADR on adopting a microservices architecture, selecting a particular cloud provider, or choosing to rewrite a legacy subsystem. The goal is to explicitly articulate the motivations, alternatives considered, and implications of significant architectural decisions.

I recommend that every architect maintain a collection of ADRs for their system, stored alongside the codebase and updated continually as new decisions are made. Each ADR should include a concise title, the status (proposed, accepted, deprecated, etc), the context in which the decision arose, the actual decision made, and any important implications or additional details worth noting. Links to related ADRs are also helpful to understand interdependent choices.

The major benefit of ADRs is that they provide a technical record that persists across time as team members come and go. Without proper documentation, important context is lost and previous decisions are rehashed over and over. New engineers can get up to speed on system design much faster by consulting the set of ADRs. When encountering confusing or suboptimal code, tracing it back to the original ADR helps explain the situation. The ADR collection also aids future decision making by revealing constraints and trade-offs that were previously considered.

From a process perspective, I recommend reviewing ADRs regularly at architecture meetings and requiring sign-off from technical leads for impactful decisions. Lightweight ADRs can be created to explore potential ideas, while more durable ADRs capture commitments going forward. Versioning allows tracking of changes and helps communicate those changes to stakeholders. There are also tools emerging that facilitate ADR management as part of internal developer portals.

In essence, ADRs enable the kind of structured thinking and external documentation that is essential for consistent and maintainable architectures. As systems and organizations scale, it becomes untenable for architectural knowledge to remain trapped inside individual heads. I encourage all software teams to adopt the practice of architectural decision records for the long-term health of their critical systems. Let me know if you have any other questions!