# Performance Efficiency Scenario

**In short:** A performance efficiency scenario turns a vague goal like "be fast" into a testable statement. Something triggers the system, the system reacts, and a measurable criterion says whether the reaction was good enough.

## Explanation

Teams often write performance goals such as "the system must be fast". Nobody can test that. A quality scenario fixes this. arc42 says quality scenarios make quality requirements concrete and let you decide whether they are fulfilled. They can serve as acceptance criteria.

arc42 treats performance and efficiency as a kind of usage scenario. It describes how the running system reacts to a stimulus. A stimulus is an event that hits the system, such as a user request.

Three parts of a scenario matter most for performance:

- **Artifact:** the part of the system that the stimulus affects.
- **Environment:** the conditions under which the stimulus occurs.
- **Response measure:** a measurable criterion that lets you judge objectively whether the requirement is met.

The response measure makes the scenario testable. A percentile is one example. A requirement can say the 95th percentile response time stays under 800 milliseconds. That means 95 out of 100 responses must be faster than the limit.

The simplest form is short. arc42 gives this example: the system reacts to a user's request within one second.

Performance efficiency is also a standard quality category. ISO 25010 defines it as performing functions within a specified time, with efficient use of resources. Its subcharacteristics are time behaviour, resource utilization, and capacity. They give you ideas for what to measure. See ISO/IEC 25010 Product Quality Model.

arc42 also recommends using quality scenarios to analyze or evaluate an architecture. See Quality Attribute Scenario for the general template.

## Example

An online shop team starts with the vague goal "search should be quick".

They rewrite it as a scenario. A visitor sends a search request (the stimulus). The search component is the artifact. The environment is normal daily operation. The response measure says the 95th percentile response time stays under a chosen limit.

Now a load test can show a clear pass or fail.

## Trade-offs

The facts here do not discuss costs. One point follows from the definitions: a scenario only helps if its response measure is measurable. A goal without a measurable criterion cannot be judged objectively.



## Checks

- Each performance requirement is written as a scenario with a stimulus, an affected artifact, and an environment.
- Each performance scenario has a measurable response measure, such as a time limit or a percentile.
- Performance scenarios are usable as acceptance criteria that decide whether the requirement is fulfilled.
- Performance scenarios are listed in the quality requirements section and used to evaluate the architecture.

## Related

- [Quality Attribute Scenario](https://arc.fuet.ch/concepts/quality-attributes/quality-attribute-scenario.md)
- [Performance Efficiency](https://arc.fuet.ch/concepts/quality-attributes/performance-efficiency.md)
- [Performance Tactic](https://arc.fuet.ch/concepts/tactics/performance-tactics.md)
- [arc42 Quality Requirements](https://arc.fuet.ch/concepts/documentation/arc42-quality-requirements.md)
- [Acceptance Criterion](https://arc.fuet.ch/concepts/functional-requirements/acceptance-criteria.md)
- [ISO/IEC 25010 Product Quality Model](https://arc.fuet.ch/concepts/quality-attributes/iso-iec-25010-quality-model.md)
- [Architecture Tradeoff Analysis Method (ATAM)](https://arc.fuet.ch/concepts/evaluation/architecture-tradeoff-analysis-method-atam.md)
- [Availability Scenario](https://arc.fuet.ch/concepts/quality-attributes/availability-scenario.md)

## Sources

- [10 - Quality | arc42 Documentation](https://docs.arc42.org/section-10/) — docs.arc42.org, accessed 2026-11-08
- [How to specify quality requirements | arc42 Quality Model](https://quality.arc42.org/articles/specify-quality-requirements) — quality.arc42.org, accessed 2026-11-08
- [ISO 25010](https://iso25000.com/index.php/en/iso-25000-standards/iso-25010) — iso25000.com, accessed 2026-11-08