clustering

The assign-then-update loop is ten lines; the signal is whether you handle the three things that bite in production: initialization, an empty cluster, and a real convergence test instead of a fixed iteration count.

Unsupervised questions filter out candidates who've only done Kaggle. The elbow method is the warm-up, the real scoring is on validation without labels and the marketing-team handoff.

Snowflake's signature internals question, and the trap is in the second half: most candidates can define micro-partitions, but the scoring is on knowing the four cases where scaling up burns credits for zero speedup.