Learn in the textbookFundamentals of Service Management and Service Level Management
DefinitionAn SLI (service level indicator, サービスレベル指標) is an indicator obtained by actually measuring the state of a service, and it is the basis for judging whether an SLO is being met.
ExplanationFor example, the share of time a service was actually usable in a given month, or the average measured response time, is an SLI. When comparing SLIs against SLOs reveals an item that falls short, the cause is investigated and improvements follow.
AnalogyIt is the actual time shown on the clock when you cross the marathon finish line.
Memory hookThe final I stands for Indicator, which points to the current value like the needle on a gauge.