Availability
Keeping the system up and correct despite failures — pre-existing folder, already has subtopics started.
Why we need this / what value this brings
Downtime has a direct, measurable cost — knowing your actual availability target keeps engineering effort proportional to real business impact.
When to use this
Define a target before an incident forces you to improvise one.
How to use or implement this
Pick a realistic target (99.9% is a common small-team default), instrument uptime, and only invest further once data shows it's the actual bottleneck.
Subtopics
Empty folder — drop notes, links, and findings here as you research.