Service Level Agreement (SLA)
A documented agreement between a service provider and a customer that identifies both services required and the expected level of service.
Impact
SLAs manage expectations. Without an SLA, the expectation is "100% perfection," which is impossible.
Weinto take
SLAs are for Lawyers; SLOs are for Engineers. An SLA is a financial penalty if we fail. An SLO (Service Level Objective) is the internal warning line we defend to ensure we never hit the SLA. We focus on the SLO.