SLA-VS-SLO-VS-SLI

SLI measures, SLO target, SLA contract.

Definition

SLI example: 99.9% requests < 200ms over 30d (real measurement). Internal SLO: 99.95% (stricter target). External SLA: 99.5% (with service credit if missed). Error budget = 1 - SLO. Published by Google in Site Reliability Engineering (2016).

Origin

Concepts formalised Google SRE 2003-2010 ; book Site Reliability Engineering published 2016.

Example in context

An EDI operator publishes a 99.5% availability SLA with 10% service credit if < 99% monthly.

Related terms

• Error budgets — derived from SLO.