# Error budget

> The amount of unreliability an SLO allows over a period: with a 99.9% target, 0.1% of requests may fail. Spending it slows releases; saving it allows risk.

URL: https://pagerless.dev/glossary/error-budget
Updated: 2026-10-22

## Related terms

- [SLO](https://pagerless.dev/glossary/slo): Service level objective: a target value or range for an SLI, such as 99.9% of requests succeeding over 30 days.
- [SLI](https://pagerless.dev/glossary/sli): Service level indicator: a carefully defined quantitative measure of some aspect of service, such as the share of requests served successfully.

Sources:
1. [Google SRE book, ch. 3: Embracing Risk](https://sre.google/sre-book/embracing-risk/)