SLI — Service Level Indicator

In plain English

A Service Level Indicator is a metric used to measure the actual performance of a service.

An SLI is the number behind the promise.
It’s the measurement that shows whether a service is meeting its SLO — and, indirectly, its SLA.

Think uptime percentage, response time, error rate, or latency.

What they actually mean

SLIs are where reality lives.

You can debate priorities, reinterpret goals, and soften language —
but the SLI just reports what actually happened.

When SLIs turn red, conversations quickly move from “alignment” to accountability.

Example

Does it actually matter?

Yes — absolutely.
Without SLIs, SLOs are wishes and SLAs are marketing.

SLIs enable:

• real decisions


• honest trade-offs


• meaningful reviews