What is HNSW?

HNSW (Hierarchical Navigable Small World) is an efficient algorithm for approximate nearest neighbor (ANN) search, designed to handle large-scale, high-dimensional data. It builds a graph-based index where data points are nodes, and edges represent their proximity. The algorithm organizes the graph into hierarchical layers. The top layers have fewer nodes and represent coarse-grained views of the dataset, while the lower layers have denser connections and finer granularity. During a search, HNSW starts at the top layer and navigates down, finding the nearest neighbors quickly by skipping irrelevant nodes. HNSW is valued for its balance of speed and accuracy, making it suitable for real-time applications like recommendation systems, image retrieval, and natural language queries. It’s commonly integrated into vector databases for managing embeddings efficiently.