Advanced – Non-Functional Testing
Service Level Indicator (SLI) – ISTQB Definition
Last Updated: July 12, 2026 · SoftwareTestPilot QA Team
Official ISTQB Definition
A quantitative measure of some aspect of service level, such as request latency, error rate, or availability.
In simple words
A specific metric that shows how well the service is doing.
Exam tip
SLI → SLO → SLA is the SRE reliability chain.
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