HNSW Configuration

HNSW parameter reference and configuration options

Learn about HNSW parameters and how they affect performance.

Parameter Reference

Option	Default	Description
M	16	Connections per node in layer > 0 (higher = better recall)
M0	32	Connections for layer 0 (typically M x 2)
efConstruction	200	Candidate list size during construction
efSearch	50	Candidate list size during search

M (Max Connections)

Controls the number of connections each node has in the graph.

src/hnsw-m-param.ts

// Low M (8-12) - faster build, less memory, lower recall
const fast = new VectoriaDB({
  useHNSW: true,
  hnsw: { M: 8 },
});

// High M (24-48) - slower build, more memory, higher recall
const accurate = new VectoriaDB({
  useHNSW: true,
  hnsw: { M: 32 },
});

M Impact

M Value	Build Speed	Memory	Recall
8	Fast	Low	~93%
16	Medium	Medium	~96%
32	Slow	High	~98%

efConstruction

Controls build-time quality. Higher values = better graph structure but slower indexing.

src/hnsw-ef-construction.ts

// Fast construction, acceptable quality
const quickBuild = new VectoriaDB({
  useHNSW: true,
  hnsw: { efConstruction: 100 },
});

// Slow construction, excellent quality
const highQuality = new VectoriaDB({
  useHNSW: true,
  hnsw: { efConstruction: 400 },
});

efConstruction Impact

Value	Build Speed	Index Quality
100	Fast	Good
200	Medium	Very Good
400	Slow	Excellent

efSearch

Controls search-time quality. Can be adjusted per-query:

src/hnsw-ef-search.ts

const db = new VectoriaDB({
  useHNSW: true,
  hnsw: { efSearch: 50 }, // Default
});

// High-precision search
const results = await db.search(query, {
  topK: 10,
  efSearch: 200, // Override for this query
});

// Fast search (lower recall)
const quick = await db.search(query, {
  topK: 10,
  efSearch: 20,
});

efSearch Impact

Value	Search Speed	Recall
20	Very Fast	~92%
50	Fast	~96%
100	Medium	~98%
200	Slow	~99%

Configuration Presets

src/hnsw-presets.ts

// Speed-optimized (95%+ recall)
const speedOptimized = {
  M: 12,
  efConstruction: 100,
  efSearch: 30,
};

// Balanced (97%+ recall)
const balanced = {
  M: 16,
  efConstruction: 200,
  efSearch: 50,
};

// Quality-optimized (99%+ recall)
const qualityOptimized = {
  M: 32,
  efConstruction: 400,
  efSearch: 100,
};

Full Configuration Example

src/hnsw-full-config.ts

const db = new VectoriaDB<ToolDocument>({
  useHNSW: true,
  hnsw: {
    M: 16,              // Connections per node
    M0: 32,             // Layer 0 connections (optional)
    efConstruction: 200, // Build quality
    efSearch: 50,       // Search quality
  },
  maxDocuments: 100000,
  maxBatchSize: 1000,
});

Related

HNSW Overview

Introduction to HNSW

HNSW Tuning

Tune for your use case

Search Performance

General performance tips