PSI, KL divergence, MMD, and the KS test all detect drift. When do you reach for each?

Four drift tests, four different assumptions. The weak answer lists them; the strong one knows which handles high-dimensional embeddings, which needs binning, and which gives a calibrated p-value. Here is how to choose.

Updated Aug 2026 · Grounded in real Applied AI Engineer interview loops and written to a senior-engineer editorial bar.