Service Level Indicator
A measurable metric that indicates service performance, used to track SLOs.
A measurable metric that indicates service performance, used to track SLOs.
## The "Yardstick" **SLI (Service Level Indicator)** is the specific metric you measure to see if you are meeting your goals. It is "What is happening right now?" ### Good vs. Bad SLIs * **Bad (System-Centric)**: "CPU Usage < 80%." (Users don't care about CPU). * **Good (User-Centric)**: "Homepage Load Time < 200ms." (Users notice this). ### The Formula Most SLIs are tracked as a ratio of **Good Events** to **Total Events**. ```math SLI = (Number of Successful Requests) / (Total Number of Requests) ``` If you have 100 requests and 1 error, your SLI is 99%.
ExThe Search Bar
"A team defined their SLI as "Search results returned"."
Why SLI Matters
SLIs are the raw metrics (latency, error rate, throughput) that feed into SLO calculations.
Good SLIs are user-focused, not system-focused. Measure what users experience.