Reliability & operations · Glossary term
What is Availability?
The proportion of eligible service interactions or time windows in which users can obtain the defined acceptable service under a stated measurement boundary.
Why does Availability matter?
A service can be running while users still cannot complete useful requests, so availability must be tied to user-visible success rather than process uptime alone.
Availability in practice
Define eligible events and acceptable outcomes, exclude only documented cases, calculate the indicator over a fixed window, and investigate both total failures and prolonged partial degradation.
What is the common confusion about Availability?
Availability is one reliability outcome. It does not describe latency, correctness, safety, or the experience of every user segment.
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Related terms
- Service Level Indicator (SLI)A quantitative measure of service behavior at a defined user-relevant boundary, such as successful request ratio or latency below a…
- Service Level Objective (SLO)A target range or threshold for a service-level indicator over a stated population and measurement window.
- Error BudgetThe amount of unsuccessful service allowed by a service-level objective over its measurement window before the objective is exhausted.
- Incident ResponseThe coordinated process for detecting, analyzing, containing, recovering from, communicating, and learning from an event that threatens…
- Graceful DegradationPreserving a bounded core service when capacity or dependencies are impaired by reducing optional quality, features, freshness, or…
- Readiness ProbeA diagnostic that tells the traffic-routing layer whether a service instance is currently able to accept requests.
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