hierarchical

k-means is the reflex answer, but it quietly assumes round, equal-size clusters and demands you know k upfront. The signal is positioning each alternative by the exact assumption it removes, and knowing when to reach for it.

Forecasting one series is a textbook exercise; forecasting a million SKU-stores that must reconcile, with stockouts costing more than overstock, is the real interview. The strong answer goes global, hierarchical, and cost-aware.