SLOs

A service level objective states the reliability you are targeting, and tracks how much of your allowance for failure you have left.

Defining onelink

An SLO pairs an objective (say 99.9% of requests succeed) with a window (say 30 days). The gap between your target and 100% is the error budget: the amount of failure the objective tolerates.

Error budgetlink

Budget remaining is more actionable than the raw success rate. A healthy percentage with the budget nearly gone means you have been burning it steadily and the next incident breaches the objective.

Set objectives you would genuinely act on. An SLO nobody changes their behaviour for is a chart, not an objective.