Service Level Indicator

Service Level Indicator — A quantitative measurement of service behavior, such as availability, latency, correctness, or durability, used to evaluate an objective.

Reliability Context

A service-level indicator is the measured behavior used to evaluate reliability, such as the fraction of successful requests completed under 300 ms. A useful SLI defines both the eligible event population and the condition that counts as success.

Measurement Boundary

Infrastructure metrics such as CPU utilization are not usually direct SLIs because they do not state what the user experienced. They can explain an SLI but should not replace a user- or service-visible outcome without a clear reason.

Related Reliability Concepts

• Service Level Objective
• Error Budget
• Reliability
• Latency