SLI/SLO/SLA

Definitions

1. Three related reliability concepts: SLI (Service Level Indicator) is the metric measured (e.g., request latency p99). SLO (Service Level Objective) is the target for that metric (e.g., p99 < 200ms, 99.9% of the time). SLA (Service Level Agreement) is the contractual commitment with consequences for violations (e.g., service credits). SLI ⊂ SLO ⊂ SLA.

   In plain English: SLI is what you measure, SLO is the target you aim for, and SLA is the promise you make to customers with penalties if you miss.

   Example: "Our SLI is error rate, the SLO is < 0.1% errors over 30 days, and the SLA promises 99.9% uptime or we refund 10% of the bill."

Related Terms

• Five Nines
• MTTR
• MTTF
• MTBF
• Failover
• Active-Active
• Error Budget
• Chaos Budget
• Error Budget Culture