# Agile Architecture

**In short:** Agile architecture means doing just enough architecture, guided by the biggest risks, and revisiting it as the product changes. It avoids both big upfront design and no design at all.

## Explanation

Agile teams build in small steps. Architecture work has to fit that pace. Two extremes are best avoided: designing everything up front, and not designing at all.

**Why no design fails.** Evolutionary design means letting the design emerge as code grows. Fowler argues it fails without design effort. The design turns into a pile of ad-hoc, short-term decisions. He names a lack of will to design as a major cause of failure. He also links decaying design to a shrinking ability to change software effectively. That is close to the later idea of technical debt (see *Technical Debt*). Fairbanks says skipping design is impractical when the risk of failure is high.

**Why full upfront design is not the answer.** Fowler supports a broad starting-point architecture, not a complete one. SAFe cites Coplien: design will partly emerge, yet a little planning avoids much waste.

**Just enough, driven by risk.** Fairbanks' risk-driven model ties architecture effort to the risk of failure. You do three things:

- Prioritize the risks.
- Apply techniques that reduce them.
- Check the outcome.

You design only the riskiest parts. This often takes hours or days, not months. The model works with waterfall or agile processes.

**Tailor the models.** A model here is an architectural viewpoint (see *Architecture Viewpoint*). Decide in advance which questions it must answer. If throughput is the main worry, build a throughput model.

**Runway and intentional architecture.** SAFe asks agile architects to keep just enough architectural runway in place for evolving business needs. The architects' set of intentions is called the intentional architecture. The runway is not a one-time exercise. It is updated as the product changes, so architecture work stays a continuous cycle.

## Example

A team starts a new online shop. In a short session they list their biggest risks. One risk is that checkout may be too slow during sales. They build a small throughput model, which answers one question: can checkout handle the expected load? They skip detailed design for low-risk parts, such as the help pages. As the product grows, they revisit the risk list and update their architectural intentions.

## Trade-offs

Doing just enough architecture saves time and avoids waste. But it needs discipline. If the team lacks the will to design, the design can degrade into ad-hoc decisions. If the team misjudges the risks, it may skip design that mattered. Keeping the runway and the risk list current also takes continuing effort.

A risk-driven cycle of just enough architecture

```mermaid
flowchart LR
  A[Prioritize risks] --> B[Apply techniques that reduce them]
  B --> C[Check the outcome]
  C --> D[Build and update the runway]
  D --> A
```

## Checks

- The document names the main project risks and ties architecture effort to them.
- Models or viewpoints are chosen to answer stated questions, such as a throughput model for a throughput concern.
- The document shows some deliberate design effort rather than only ad-hoc tactical decisions.
- The architectural runway or intentions are kept current as the product changes.
- The design describes a broad starting-point architecture, not a complete upfront design.

## Related

- [Risk Storming](https://arc.fuet.ch/concepts/evaluation/risk-storming.md)
- [Technical Debt](https://arc.fuet.ch/concepts/evaluation/technical-debt.md)
- [Architectural Thinking](https://arc.fuet.ch/concepts/fundamentals/architectural-thinking.md)
- [Continuous Architecture Principles](https://arc.fuet.ch/concepts/principles/continuous-architecture-principles.md)
- [Last Responsible Moment](https://arc.fuet.ch/concepts/forces-decisions/last-responsible-moment.md)
- [Iterative and Incremental Development](https://arc.fuet.ch/concepts/fundamentals/iterative-and-incremental-development.md)
- [Architecture Viewpoint](https://arc.fuet.ch/concepts/documentation/architecture-viewpoint.md)
- [Architecture Decay](https://arc.fuet.ch/concepts/fundamentals/architecture-decay.md)

## Sources

- [Extended Guidance - Agile Architecture in SAFe - Scaled Agile Framework](https://framework.scaledagile.com/agile-architecture/) — framework.scaledagile.com, accessed 2026-11-09
- [Is Design Dead?](https://www.martinfowler.com/articles/designDead.html) — martinfowler.com, accessed 2026-11-09
- [](https://www.methodsandtools.com/archive/agilearchi.html) — methodsandtools.com, accessed 2026-11-09
- [Architecture Runway – Aligning Intentional and Emerging Design](https://continuous-architecture.pages.dev/practices/architecture-runway/) — continuous-architecture.pages.dev, accessed 2026-11-09
- [Interview and Book Excerpt: George Fairbanks’ Just Enough Software Architecture - InfoQ](https://www.infoq.com/articles/fairbanks-jesa/) — infoq.com, accessed 2026-11-09