# Architecture Principle

**In short:** An architecture principle is a short statement of what an organization values. It narrows the options for design decisions without dictating the answer, so teams decide faster and more consistently.

## Explanation

An architecture principle is a guideline for a whole class of problems. It is cohesive, prescriptive and supports decisions. It does not name the solution. It limits the range of options, like a guardrail rather than a gate. That limit helps teams decide faster.

**Principles and decisions.** Principles record the priorities and beliefs that guide reasoning. Decisions are the actual unit of architectural work (see Architectural Decision). A principle justifies a decision. It also restricts how the architecture is designed, while the requirements are still met.

**Reflect real values.** A good principle shows what the organization values most when it must compromise. It therefore depends on the organization's context. A generic statement that fits everyone says little.

**How to write one.** A useful formulation has five parts:

- the statement itself;
- the rationale, which should tie to stakeholders and their goals;
- the consequences;
- the exceptions, meaning situations where deviation is acceptable;
- the relations to other principles.

The rationale should support discussion. See Architecture Principle Structure for details.

**Exceptions and review.** Sometimes a team sets a principle aside for good reasons. If that happens repeatedly, the principle may need a review. One source suggests three justified exceptions as a trigger.

**In arc42.** The solution strategy lists the key decisions that form the cornerstones of the architecture. It should keep them short, motivated and justified. Principles fit naturally there. See Solution Strategy.

## Example

A company states this principle: "Prefer packaged products over custom code." The rationale says the business wants features quickly and has a small team. A consequence is that teams must justify any custom build. An exception covers a feature that gives the company a unique edge. When a team plans a new billing function, the principle removes "build from scratch" as the default option. The team then compares packaged products.

## Trade-offs

Principles involve trade-offs. For example, a principle that favors packaged solutions saves effort. But heavy customization of such packages raises maintenance costs. Teams need to balance the two. A principle that is too rigid can also block sensible choices. Listing exceptions, and reviewing a principle when exceptions pile up, keeps it useful.



## Checks

- Each principle has a statement, a rationale tied to stakeholder goals, consequences, exceptions and relations.
- The principles reflect what the organization values when it must compromise, not generic statements.
- Principles narrow the options instead of dictating a single answer.
- Repeated justified exceptions to a principle trigger a review of it.

## Related

- [Architecture Principle Structure](https://arc.fuet.ch/concepts/principles/structure-of-an-architecture-principle.md)
- [Working with Principles](https://arc.fuet.ch/concepts/principles/working-with-principles.md)
- [Conflicting Architecture Principles](https://arc.fuet.ch/concepts/principles/conflicting-architecture-principles.md)
- [Continuous Architecture Principles](https://arc.fuet.ch/concepts/principles/continuous-architecture-principles.md)
- [Architectural Decision](https://arc.fuet.ch/concepts/forces-decisions/architectural-decision.md)
- [Solution Strategy](https://arc.fuet.ch/concepts/documentation/arc42-solution-strategy.md)
- [Data Architecture Principle](https://arc.fuet.ch/concepts/enterprise-architecture/data-architecture-principle.md)
- [Relationships Between Architecture Principles](https://arc.fuet.ch/concepts/principles/relationships-between-architecture-principles.md)

## Sources

- [Why Principles and Decisions Are the Core of Modern Software Architecture – Continuous Architecture in Practice](https://continuousarchitecture.com/2025/11/15/why-principles-and-decisions-are-the-core-of-modern-software-architecture/) — continuousarchitecture.com, accessed 2026-11-09
- [Fundamentals for architecture principles (part1) - Sogeti Labs](https://labs.sogeti.com/fundamentals-for-architecture-principles-part1/) — labs.sogeti.com, accessed 2026-11-09
- [IT Architecture Principles](https://www.itarch.info/2020/01/it-architecture-principles.html) — itarch.info, accessed 2026-11-09
- [4 - Solution strategy | arc42 Documentation](https://docs.arc42.org/section-4/) — docs.arc42.org, accessed 2026-11-09