Three related concepts for managing reliability:
SLI (Service Level Indicator):
The metric you measure. Example: request latency P99, error rate, availability.
SLO (Service Level Objective):
Your internal target. Example: P99 latency < ms, availability > %.
SLA (Service Level Agreement):
Contractual commitment to customers. Usually lower than SLO (buffer for safety). Includes penalties for violations.
Set SLO stricter than SLA. If SLO is %, SLA might be %.