An architecture diagram can show what connects to what. It may leave out why those connections exist.
That reasoning matters when a new team joins, a business requirement changes, or someone proposes a different approach. Without it, people have to reconstruct the decision from the system they inherited.
I favour a short written record alongside important architecture choices. Its purpose is to help the next person understand the context and judge whether the decision still fits.
Start with the constraint
Describe the problem that required a choice. Include the constraints that influenced it: delivery commitments, existing systems, operating responsibilities, or the team’s familiarity with an approach.
Use specifics where they are known. If something is still an assumption, call it an assumption.
For example, a team might choose to keep a new capability within an existing application because the same people operate both and the capability has no demonstrated need for independent deployment. That context is useful when discussing whether to separate it later.
This is an illustrative example, not a recommendation for every system.
Record the alternatives fairly
A decision record is more useful when another option receives a fair explanation.
Write down the approaches considered, the benefit each offered, and the cost or uncertainty that influenced the choice. Avoid describing the chosen option as universally better when it was simply a better fit for the current circumstances.
Also record what the team is accepting: a dependency, additional operating work, a limitation, or a question that remains open.
Define a reason to revisit
A decision does not need to be permanent to be useful.
Ask what change would justify another look. In the example above, that could be a different team taking responsibility, a need to release independently, or evidence that the current boundary is obstructing delivery.
These are review triggers, not predictions. They help distinguish a changed context from a preference for a different technology.
Keep the record small
A practical record can answer six questions:
- What problem required a decision?
- What constraints and assumptions mattered?
- Which options did we consider?
- What did we choose, and why?
- What consequences do we accept?
- When should we review it?
Add a date and a responsible owner so people know where to continue the discussion.
The record should remain close to the work and easy to find. When the decision changes, retain the earlier reasoning and explain what changed.
Good architecture communication gives the next team enough context to make its own informed decision.