When Does a Knowledge Graph Beat Vector Search — and When Do You Actually Need Neo4j? (opens in new tab)

Everyone answers questions over their data with vector search. But some questions aren't 'what's similar' — they're 'what's connected,' and vectors fall off a cliff. I measured vector search, graph traversal, and a hybrid of the two on 1,800 multi-hop movie questions, then settled the Postgres-vs-Neo4j question with real numbers: Postgres wins neighborhood reachability by ~4x, Neo4j wins shortest-path by ~85-135x. The honest answer is to match the engine to the traversal.