Data & AI

How HNSW Indexes Millions of Vectors

Data & AI Pipelines diagram · made in Skemio

Architecture diagram illustrating HNSW vector indexing layers from sparse top layer highways down to dense bottom layer local connections.
Architecture diagram illustrating HNSW vector indexing layers from sparse top layer highways down to dense bottom layer local connections.

What it shows

  • Organizes vectors into hierarchical multi-layer skip-list graph structures.
  • Top layers have sparse connections for rapid coarse-grained exploration.
  • Bottom layer (Layer 0) holds all vectors with dense local neighbor links.

The takeaway

HNSW trades small memory overhead for logarithmic nearest neighbor search speeds in high dimensions.

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