Service Level Objective
Definition
A Service-Level Objective (SLO) is a key element of a Service-Level Agreement (SLA) between a service provider and a customer. SLOs are agreed upon as a means of measuring the performance of the Service Provider.
Why It Matters
SLOs are the specific, measurable targets that a team aims to meet. They are an internal goal that is stricter than the external SLA. They are a key concept in Site Reliability Engineering (SRE) for balancing reliability with the need to innovate.
Contextual Example
A team might have an external SLA of 99.9% uptime with their customers. Internally, they set a stricter SLO of 99.95%. The difference between the SLO and the SLA is their "error budget" – the amount of downtime they can tolerate without violating their promise to customers. This budget can be "spent" on risky deployments or planned maintenance.
Common Misunderstandings
- SLOs are internal targets. SLAs are external promises.
- A well-defined SLO is specific, measurable, achievable, relevant, and time-bound (SMART).