Comparison
Service level agreementvsService level objective
Service level agreement
you promise the customer 99.5 percent in a contract with money attached if you miss it.
An externally committed reliability target with consequences, usually financial. It should be strictly looser than your internal SLO, so that you are alerted and acting long before a contractual breach. Engineers rarely need to set one; they very often need to know it is not the same thing as the SLO.
Full entry →Service level objective
you commit internally to 99.9 percent of requests succeeding over 30 days, and you now have a number that says when to stop shipping features.
A target for an SLI over a time window. Its real function is decision-making: it converts "is reliability good enough" from an argument into arithmetic. An SLO nobody is willing to act on — by slowing releases or prioritising reliability work — is a dashboard, not an objective.
Full entry →