Concepts and Definitions

SLIs, SLOs, Error Budgets, Burn Rate.
Before we delve into service level objectives and explore how you can leverage to optimize them, let's first clarify some foundational SLO concepts.
  1. 1.
    Service Level Indicators (SLIs): These measurements, expressed on a 0-100% scale, expresses a service's performance from a client's perspective. SLIs are derived from metrics gathered by monitoring systems and are evaluated against an SLO for compliance. A crutial aspect for builtind an SLO is the classification of events or interactions into good or bad according to a given quality criteria.
  2. 2.
    Service Level Objectives (SLOs): SLOs are internal commitments about an application's reliability that IT and DevOps teams aim to meet. They serve as a performance yardstick for specific metrics such as uptime or response time. An SLO is often a subset of a Service Level Agreement (SLA).
  3. 3.
    Error Budgets: These are calculated from an SLO’s target and represent the maximum permissible level of unreliability for a particular technical system within a specific time period. Error budgets can be viewed as a time cushion where failures are tolerated and can be allocated for product development, feature releases, or as a "rainy day" fund.
  4. 4.
    Remaining Error Budget: This refers to the leftover error budget an SLO has within its compliance window. For request-based SLOs, the remaining error budget is estimated based on historical request data from past compliance periods. For time-based SLOs, it's calculated using the actual error budget derived from the SLO's target for a specific compliance window.
  5. 5.
    Burn Rate: This is the rate at which an SLO’s error budget is being consumed. It illustrates how quickly a given error budget is diminishing. The burn rate value is interpreted as the portion of the SLO’s compliance window during which the error budget will be entirely depleted. For instance, a burn rate of 2 implies that at the current error rate, the error budget would fall from 100% to 0% within half (1/2) the duration of the SLO’s compliance window. A burn rate value of 5 means the error budget would be entirely depleted within a fifth (1/5) of the SLO’s compliance window.