# SLO

> Service level objective: a target value or range for an SLI, such as 99.9% of requests succeeding over 30 days.

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

## Related terms

- [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.
- [SLA](https://pagerless.dev/glossary/sla): Service level agreement: a contract with users that includes consequences for meeting or missing the SLOs it contains.
- [Error budget](https://pagerless.dev/glossary/error-budget): The amount of unreliability an SLO allows over a period: with a 99.9% target, 0.1% of requests may fail

Sources:
1. [Google SRE book, ch. 4: Service Level Objectives](https://sre.google/sre-book/service-level-objectives/)