Downtime

Definition

Downtime is the period when a service is unavailable or unusable according to your monitoring rules—typically when checks fail consecutively or critical dependencies are unreachable.

Types

• Hard downtime: Complete failure (HTTP errors, connection refused).
• Partial degradation: Elevated latency or error rates that may still breach SLAs.

Measurement

Teams often report uptime as 1 - (downtime / period) or compare against SLA windows. Be explicit about maintenance exclusions and what counts as “user-facing.”

Related terms

See uptime monitoring and SLA for how targets are defined and enforced.