Architecture documentation fails when it becomes a once-a-year deliverable that no one reads. It succeeds when it captures the reasoning behind decisions and stays synced with the code it describes.
The most valuable artifact is not the big design doc — it is a lightweight record of decisions and the context around them.
The decision record pattern
Architecture Decision Records (ADRs) are short documents that answer: what decision, what context, what options, and why this one. A few paragraphs each, they accumulate into a history your future self will thank you for.
- Number them and link decisions that depend on each other.
- Record the decision when it is made, not months later.
- State the trade-offs you accepted — that is the valuable part.
A decision without its rationale is just an opinion your successor will reverse.
Diagrams that stay true
Keep diagrams at the system level, generate them from code where possible, and mark them with a "last verified" date. A diagram that contradicts the code erodes trust in all documentation.
Know when to stop
If a doc describes something the code already expresses clearly, delete it. Duplication is worse than absence, because it drifts. The test: if a developer cannot trust the doc, it is a liability.
Documentation FAQ
Where should ADRs live?
In the repository, next to the code they affect — for example in a /docs/adr folder. Keeping them with the code means they change in the same review as the implementation.
How long should an ADR be?
Short. A few sentences of context, a decision statement, and the accepted trade-offs. Long ADRs are read once and never again.
