10.2.1 · Skill in Reliability engineering

Availability

How much of the time the product works for users.

Availability is usually expressed as a percentage of successful time or requests. Each extra nine costs much more than the last. The right target depends on what users need, not on what sounds impressive.

Your status · Availability

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Resources

bookStart here
Embracing risk (Site Reliability Engineering, chapter 3) ↗
Google SRE · 20 min
Why 100% reliability is the wrong target, and how error budgets balance reliability with shipping.

Tools

ToolOpen source
Uptime Kuma
github.com ↗
Self-hosted uptime monitoring with status pages and notifications.