Error Rate Burn vs Error Budget Burn

Two related but distinct concepts. Error rate is the per-time-unit error count; budget burn is the cumulative against SLO.

Error rate

Errors per minute, errors per request. Useful for short-term alerting.

Spike-driven: a burst of errors fires the alert.

Budget burn

Errors as a fraction of allowed errors over the SLO window.

Cumulative: small errors accumulating over hours can exhaust the budget without firing rate alerts.

Use both

Rate alerts: 'something is happening right now.'

Burn alerts: 'we are heading toward SLO violation by end of period.' Both are essential.