SLI (Service Level Indicator): A metric that measures service behavior. Examples: request latency, error rate, availability.
SLO (Service Level Objective): A target value for an SLI. Example: "% of requests complete in under ms."
SLA (Service Level Agreement): A contract with consequences for missing the SLO. Usually involves refunds or credits.
Relationship:
SLI (what you measure) → SLO (your target) → SLA (customer promise)
Interview question: "Define SLI, SLO, and SLA with examples."
SLI: Percentage of requests returning status. SLO: % success rate. SLA: Credits if we miss %.