Glossary · Phase 11 · Professional practice
Error budget
The failures an SLO allows, such as 0.1% of requests. While budget remains, ship; when it's spent, focus on reliability.
An SLO of 99.9% means 0.1% of requests may fail. That 0.1% is the error budget, and it works like a monthly allowance that you spend on taking risks.
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A burn rate of 1 uses the budget exactly over 30 days. A burn rate of 10 uses it in 3 days, and that's worth waking someone up for.
Learn it properly
Reliability and incidents · SLOs, error budgets, alerts, on-call and blameless postmortems. About 40 minutes.
Other terms from the same lesson
- blameless postmortem: A write-up after an incident that looks for how the system allowed it, not who to blame, and ends with owned action items.
- burn rate: How fast the error budget is being used, compared with the pace that would last exactly the whole period.
- incident commander: The person who coordinates an incident response and makes decisions, while others do the hands-on work.
- runbook: Written steps for handling an alert or task: what it means, how to check, what to try first.
- SLO: A reliability target for something users feel, such as 99.9% of requests succeeding fast, measured by an indicator (SLI).
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