reliability
Error budget
Error budget: the slice of allowed unavailability under an SLO (e.g. 99.9 % over 30 days = ~43 minutes of allowed downtime).
Definition
The error budget is (1 − SLO target) × time window. It is the absolute amount of unavailability (or latency violation, error-rate violation, …) allowed before the SLO is breached. The complement is uptime. In operations, what matters is how fast you consume the budget.
In MaxoPerf
Use error budgets to decide whether a performance regression is acceptable. If a load test shows latency or error rates that would consume the budget too quickly, the release should pause even if average response time still looks healthy.
Common pitfalls
- Picking a 99.99 % target without the budget to back it up. Every minute of unavailability is a 1 % monthly hit.
- Treating the budget as a target floor rather than a budget to spend on releases, planned maintenance, and migrations.
FAQ
How is the error budget calculated?
(1 − SLO target) × window. 99.9 % over 30 days = ~43 min; 99.95 % over 30 days = ~22 min.
What is a burn-rate alert?
An alert that fires when you consume the budget faster than the window allows. Burning 1 hour of budget in 15 minutes is a critical pager event even if the dashboard still says "99.9 %".
