SLA / SLO / SLI

SLO: Service Level Objective #

An SLO is a specific, measurable goal or target that a service aims to achieve. It is a component of an SLA and defines the acceptable level of service.

An example of this can be the availability of a service. It is quite common to aim for something like 99.9% uptime as one of the SLO of a service.

TL;DR: Target level of service that the provider aims to achieve.

SLA: Service Level Agreement #

An SLA is a formal agreement between a service provider and a customer that outlines the expected level of service. It typically includes one or more SLOs and details what happens if these targets are not met, including any penalties or compensations.

An example of this might be an SLA specifying multiple SLOs, one being for instance the 99.9% availability. And on the failure to meet this objective, the service provider may need to refund a portion of the customer’s fees as specified in the SLA.

TL;DR: Agreement that defines the SLOs and the consequences.

SLI: Service Level Indicator #

An SLI is a specific metric used to measure the performance of a service. It quantifies how well the service is performing against the defined SLOs.

An example of this might simply be the actual uptime percentage measurement of a service in a month (e.g 99.95% uptime)

TL;DR: Metric used to measure the performance of the service.