Metrics
What's measured to know the system is healthy — RED method (Rate/Errors/Duration) or USE method (Utilization/Saturation/Errors).
Why we need this / what value this brings
Metrics answer 'is the system healthy right now' at a glance, without digging through logs.
When to use this
From the start for anything you'd want to know is broken before a user reports it.
How to use or implement this
Track the RED method for request-driven services (Rate, Errors, Duration) as a baseline before adding custom business metrics.
Empty folder — drop notes, links, and findings here as you research.