---
title: "Service Level Objective (SLO) — monitoring glossary"
description: "SLO means Service Level Objective — the internal reliability target a team commits to, such as 99.9% of homepage requests returning in under 400ms over a…"
canonical: "https://lemwatch.com/glossary/slo"
source: "https://lemwatch.com"
---

# Service Level Objective (SLO)

> SLO means Service Level Objective — the internal reliability target a team commits to, such as 99.9% of homepage requests returning in under 400ms over a rolling 30-day window. SLOs sit inside the SLA envelope and give engineering the numbers to code, alert,…

## Definition

 SLOs are the operational form of the SLA. Where the SLA promises the customer 99.5% uptime, the internal SLO is usually stricter (99.9%) so there is headroom before contract penalties kick in.

 Each SLO has a service level indicator (SLI) that measures it — availability, latency, error rate, freshness. When the SLI drops below the SLO, the error budget shrinks; when it burns out, deploys freeze until reliability is restored.

## Why it matters

 SLOs replace argument with math. Instead of 'is this outage bad?' the team asks 'did this outage burn our error budget?'. That reframes reliability from vibes to a shared, quantitative constraint — and stops feature velocity from silently degrading uptime.


## Related

- [Monitoring glossary](https://lemwatch.com/glossary)
- [SLA](https://lemwatch.com/glossary/sla)
- [Error Budget](https://lemwatch.com/glossary/error-budget)
- [Service Level Indicator](https://lemwatch.com/glossary/sli)
- [Uptime](https://lemwatch.com/glossary/uptime)
- [All monitoring checks](https://lemwatch.com/features)
- [SPF (Sender Policy Framework)](https://lemwatch.com/glossary/spf)