Vector Databases in Depth

Exact nearest neighbour search is intractable at scale and k-d trees collapse above a couple of dozen dimensions, so every production system trades recall for speed. This cursus covers that trade properly. Why the classical indexes fail and how to measure recall against brute-force ground truth. Then HNSW as a navigable small-world graph, IVF as partition-and-probe, and the quantization schemes that decide your infrastructure bill. Then hybrid search, a tuning method that starts from a stated target, capacity planning, and the operational failures no benchmark shows.