Debugging & Diagnosis Models

Mental models for finding the cause of problems.

Model	One-Liner
USE Method	Check Utilization, Saturation, Errors for every resource
RED Method	Measure Rate, Errors, Duration for every service
Five Whys	Ask "why" five times to reach root cause
Bisect	Binary search for the breaking change
Differential Diagnosis	Enumerate and eliminate hypotheses systematically
Correlation vs Causation	The deploy preceded the outage -- but did it cause it?

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• Mental Model Library
• Mental Model: Bisect
• Mental Model: Correlation vs Causation
• Mental Model: Differential Diagnosis
• Mental Model: Five Whys
• Mental Model: RED Method
• Mental Model: USE Method