AI engineering glossary · RAG vector search
What is HNSW?
HNSW (also called Hierarchical Navigable Small World): Hierarchical Navigable Small World, a graph-based index where each vector links to nearby vectors across several layers. Search starts at a sparse top layer and greedily hops toward the query, descending to denser layers. It gives fast, accurate search but uses substantial memory.
HNSW: an example
With HNSW, a query over 10 million vectors visits roughly a few hundred nodes rather than all 10 million.
Related terms
More RAG vector search terms
Where you learn it
HNSW is part of the AI Engineering Program, which teaches it with notes, a hands-on lab and an exam. The first lesson is free.