Error Budget
Error Budget
An error budget is the acceptable amount of unreliability for a service, calculated as 100% minus the SLO target. It provides a framework for balancing reliability with development velocity.
The Error Budget Concept
If your SLO is 99.9% availability, your error budget is 0.1%: - That's ~43 minutes per month of allowed downtime - You can "spend" this budget on risky releases, experiments, or incidents
Why Error Budgets Work
They align incentives:
Without error budgets: - Ops wants stability → no changes - Dev wants features → more changes - Conflict!
With error budgets: - Both teams share a budget - If budget is healthy → ship faster - If budget is exhausted → focus on reliability - Alignment!
Using Error Budgets
Budget remaining: - Ship that risky feature - Experiment with new technology - Move fast
Budget exhausted: - Freeze non-critical changes - Focus engineering on reliability - Conduct thorough testing
Error Budget Policies
Define what happens when budget is spent: - Feature freeze until budget recovers - Additional testing requirements - Post-incident review for any further incidents - Executive notification
Calculating Error Budget
Monthly availability budget (SLO = 99.9%): - Total minutes: 30 days × 24 hours × 60 min = 43,200 min - Error budget: 0.1% × 43,200 = 43.2 minutes
If you've had 30 minutes of downtime: - Remaining budget: 43.2 - 30 = 13.2 minutes - Budget consumed: 69%