SLA vs SLO vs SLI: what's the difference and why it matters

Short summary

SLIs measure actual service performance (availability, latency, error rate). SLOs set stricter internal targets based on those metrics, with a 20-40% safety buffer. SLAs formalize targets into customer contracts with legal and financial consequences, creating a three-layer system that prevents reactive firefighting.

• •SLI = what you measure (actual performance metrics)
• •SLO = what you target internally (stricter than SLA commitments)
• •SLA = what you promise customers (with breach penalties, regulated in finance)

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