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OpenSearch:HNSW (Hierarchical Navigable Small World) configuration

Last Updated:Aug 21, 2026

HNSW index build parameters

Parameter name

Type

Default value

Description

proxima.hnsw.builder.max_neighbor_count

uint32

100

Specifies the maximum number of neighbors for a node in the graph. A larger value improves graph connectivity but also increases the graph construction cost and index size.

proxima.hnsw.builder.efconstruction

uint32

500

Controls the size of the neighbor scan area during graph construction. A larger value improves the quality of the offline graph but slows down index building. Start with a value of 400.

proxima.hnsw.builder.thread_count

uint32

0

The number of threads to use for building the index. If set to 0, the number of CPU cores is used.

HnswSearcher

Parameter name

Type

Default value

Description

proxima.hnsw.searcher.ef

uint32

500

Controls the size of the subgraph to scan during online retrieval. A larger value increases the retrieval rate but degrades performance. The recommended value range is [100, 1000].

proxima.hnsw.searcher.max_scan_ratio

float

None

Controls the ratio of points to scan during online retrieval. A larger value increases the retrieval rate but degrades performance.

proxima.hnsw.searcher.brute_force_threshold

uint32

None

Controls the minimum number of points to scan during online retrieval. If this value is greater than the number of documents in a single shard, the query degrades to a brute-force search.