CodingLevel 5
Observability
Easynot started
Mediumnot started
Hardnot started
A/b variant regressionShip the new model to a slice of traffic, watch the live metric per variant, and pull it back the moment the candidate quietly drifts below the control.4 minCron failures (silent drops)When your nightly billing script fails silently and you lose $10,000.3 minLabel delayWhen the ground truth arrives too late to train your machine learning model.3 minOnline-offline skewWhen your ML model gets an A+ in the lab, but immediately fails in production.3 minSecret logged at scaleOne careless log line carries a live secret, and your logging pipeline faithfully copies it everywhere.5 minSilent backup failureThe worst disaster is discovering your backups don't actually work.3 min