Silent-failure triage

Most production incidents are not a red alert nobody noticed. They are a green signal that was never capable of turning red. This skill is for the class of failure where every surface you own reports healthy and the thing is, nonetheless, dead.

The one rule

Before you believe any check, ask: what would this check return if the system were broken?

If the answer is "the same thing it is returning now", you have measured nothing. That check is decoration. This single question resolves more incidents than any dashboard, and it is the rule the rest of this skill is built from.

Corollaries you should say out loud while debugging: