# Seven Types of Architectural Decisions

**In short:** A decision is architectural when its effects reach beyond one place. Technology choice, such as buy versus build, is one kind of such decision. Tactics are decisions too, and the reasoning behind all of them needs recording.

## Explanation

A decision counts as architectural when its consequences are nonlocal. That means it affects more than the spot where you make it. Such decisions are made early, reach far, and are hard to change later. See Architectural Decision and Architecturally Significant Decision.

Technology choice is one kind of architectural decision. Buy versus build is a good case. The source calls it one of the most important decisions an architect makes. It affects total cost of ownership, which is the full cost of a solution over its life, not just the purchase price.

Decisions also come from quality goals. Tactics are design decisions that influence how a system controls its response to a quality concern. A tactic is simpler than a pattern. Think of a tactic as an atom and a pattern as a molecule. See Architectural Tactic and Architectural Pattern vs. Design Pattern.

Documentation matters too. You should record the rationale, meaning the reasons behind a decision. How much you record should depend on risk. If nobody records the reasons, structures such as layering can erode over time. See Architecture Decision Rationale and Architecture Decay.

## Example

A team must choose between buying a payment component and building one. The choice touches cost and every part that uses the component, so its effects are nonlocal. The team records why they chose as they did. The record is detailed because the risk is high. Later, a new developer reads it and keeps the layers intact.

## Trade-offs

Documenting rationale costs effort. The source advises basing what, when and how to document on risk. Writing down everything is not the goal. Skipping the record for risky decisions invites erosion.



## Checks

- Each decision with far-reaching, hard-to-change effects is recorded as an architectural decision.
- Buy-versus-build decisions state their total-cost-of-ownership consequences.
- The rationale for risky decisions is documented, with effort matched to risk.

## Related

- [Architectural Decision](https://arc.fuet.ch/concepts/forces-decisions/architectural-decision.md)
- [Architecturally Significant Decision](https://arc.fuet.ch/concepts/forces-decisions/architecturally-significant-decision.md)
- [Architectural Tactic](https://arc.fuet.ch/concepts/tactics/architectural-tactic.md)
- [Architecture Decision Rationale](https://arc.fuet.ch/concepts/forces-decisions/architecture-decision-rationale.md)
- [Architectural Decision Record](https://arc.fuet.ch/concepts/forces-decisions/architectural-decision-record.md)
- [Architecture Decay](https://arc.fuet.ch/concepts/fundamentals/architecture-decay.md)
- [arc42 Architecture Decisions](https://arc.fuet.ch/concepts/documentation/arc42-architecture-decisions.md)
- [Architecture as Set of Design Decisions](https://arc.fuet.ch/concepts/forces-decisions/architecture-as-set-of-design-decisions.md)

## Sources

- [2.5 Design Concepts: The Building Blocks for Creating Structures | Architectural Design | InformIT](https://www.informit.com/articles/article.aspx?p=2738304&seqNum=5) — informit.com, accessed 2026-11-09
- [2.7 Summary | Architectural Design | InformIT](https://www.informit.com/articles/article.aspx?p=2738304&seqNum=7) — informit.com, accessed 2026-11-09
- [2.6 Architecture Design Decisions | Architectural Design | InformIT](https://www.informit.com/articles/article.aspx?p=2738304&seqNum=6) — informit.com, accessed 2026-11-09