Service-level objectives (SLOs) are reliability targets for technology products and services. Service-level indicators (SLIs) are the measurements that are compared against those reliability targets. Both SLIs and SLOs are vital to the broader service-level management ecosystem of any organization.
Each SLI should be measured over a set time period and benchmarked against a corresponding SLO to set a minimum threshold for these targets.
Think of an SLO as a goal or ideal condition for a service to reach, such as 99.999% uptime. A mark on a dashboard would indicate the SLO at 99.999%. In this case, the SLI would be the needle on the dial that varies over a period of time. If that needle (the SLI) dips below the mark (the SLO), the system alerts the site reliability engineer to take action.
SLOs are widely used to measure the performance and reliability of various SaaS products, such as web hosting uptime, cloud storage availability and the latency or responsiveness of various cloud application hosting services.
Here are some typical SLI applications you’re likely to encounter:
SLIs can also be used to gauge human performance. For example: service desk responsiveness and escalation level.