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Reliability Metrics

Uptime percentage

Uptime percentage is availability expressed as a percentage of eligible monitored time.

What is uptime percentage?

Uptime percentage describes availability expressed as a percentage of eligible monitored time. In reliability work, the label is useful only when it maps to a measurable check, a clear owner, and a next action when expectations break. Without that operational meaning, the phrase becomes decoration in dashboards and status updates.

Why it matters

Uptime percentage matters because teams need a precise shared meaning for availability expressed as a percentage of eligible monitored time. Vague language turns incidents into arguments about words instead of fixes.

When everyone uses the same definition, alerts, status updates, and post-incident reviews stay aligned.

How it works

In practice, availability expressed as a percentage of eligible monitored time shows up as a concrete signal you can measure or communicate. Operators define what good looks like, watch for deviations, and record what happened when expectations break.

The useful version of uptime percentage is operational: it changes who gets notified, what customers see, or which metric a team reviews after an incident.

Practical example

Imagine a team operating around 99.95% uptime for the API component. When observed behavior stops matching the definition of uptime percentage, the team treats that change as a reliability event with a clear owner and next step.

Common misconception

Uptime percentage is automatically an SLA credit

That reading usually collapses distinct ideas into one slogan. Keep uptime percentage tied to observable behavior so the definition stays useful under pressure.

How Fajita handles this

Uptime percentage is a metric. An SLA is a contract. Do not confuse them.

Uptime and downtime examples

Approximate downtime for common uptime targets. Exact values change with month length and leap years.
UptimeApprox. downtime per 30-day monthApprox. downtime per year
99%7 hours 12 minutes3 days 15 hours 39 minutes
99.9%43 minutes 12 seconds8 hours 45 minutes 58 seconds
99.95%21 minutes 36 seconds4 hours 22 minutes 59 seconds
99.99%4 minutes 19 seconds52 minutes 36 seconds

Month figures use a 30-day month. Year figures use 365.25 days. Organizations may define eligible time differently.

Uptime percentage

Uptime percentage = Eligible available time ÷ Eligible monitored time × 100
  • Define eligible time, including whether maintenance is excluded.
  • Define how missing data is handled.
  • Different providers calculate differently; compare methodologies before comparing numbers.

Related documentation

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