Concept Drift & Performance Decay

Day 74 of 100 Days of MLOps. Data drift watches the inputs — but it's only a proxy. Sometimes the inputs look completely unchanged while the model quietly falls apart, because the relationship between inputs and outputs shifted underneath it. That's concept drift, and it's invisible to PSI and KS. You'll watch a model whose input drift reads 'all clear' while its real error climbs from $11,940 to $119,816 — and learn why tracking realized performance is the only ground truth of decay. Runs 100% locally on any OS.