An SLI is the measurement, an SLO is the internal target for it, and an SLA is the external promise to a customer, usually with penalties. SLOs are set tighter than SLAs so teams can act before a contract is breached.
Side by side
| SLI | SLO | SLA | |
|---|---|---|---|
| What it is | A measurement | An internal target | A contractual promise |
| Example | 99.95% of requests succeeded | 99.9% over 30 days | 99.5% a month or service credits |
| Owned by | Engineering | Engineering and operations | Business and legal |
| If missed | Nothing by itself | Error budget policy applies | Penalties or credits |
SLI · measuredSLO 99.9% · internal targetRoom to actSLA 99.5% · contract