Glossary · Reliability & operations
Service Level Indicator (SLI)
A quantitative measure of service behavior at a defined user-relevant boundary, such as successful request ratio or latency below a threshold.
Why it matters
Reliability discussions become actionable only when the observed behavior, eligible events, and measurement point are explicit.
In practice
Define numerator, denominator, exclusions, data source, and aggregation window, then validate that the indicator tracks an outcome users actually experience.
Common confusion
An SLI is the measurement. An SLO is the target applied to that measurement over a defined period.
Related terms
Sources
Browse the learning paths to see this term in context — every lesson is free to read.