When the Ground Shifts Beneath Your Model: A Practitioner's Guide to Distribution Shift in Production ML Systems
A model that scores impressively on held-out test data can degrade silently once it encounters the real world — not because of a coding error, but because the statistical properties of the environment it operates in have changed. Distribution shift is among the most consequential and least-monitored failure modes in applied machine learning. This guide breaks down its principal forms, illustrates each with concrete US-context examples, and provides a structured monitoring checklist for productio