SLA

A Service Level Agreement (SLA) is an **external** commitment—often contractual—to customers about availability, latency, or support response. It usually references measurable SLIs and defines remedies (credits, penalties) when breached.

| Concept | Audience | |---------|----------| | SLI | Measurement | | SLO | Internal engineering target | | SLA | Customer/legal promise |

Engineering SLOs should be stricter than published SLAs to leave buffer for measurement differences and incident duration. Sales promises must align with what observability can prove.

On interviews: who defines SLA vs SLO, credit calculations, and multi-tenant reporting.

Common pitfalls: marketing SLA without engineering input; SLI definitions customers cannot verify; hiding SLO misses that already threaten SLA.

The trade-off is competitive sales promises versus operational and financial risk when incidents occur.

Checklist:

• Keep internal SLO tighter than external SLA.
• Document SLI measurement method.
• Run game days against SLA math.
• Escalate when error budget threatens SLA buffer.