# similarity-search

High-recall Postgres vector search at billion scale

VectorChord is a Postgres extension from TensorChord that brings high-recall vector search to PostgreSQL. As the spiritual successor to pgvecto.rs, it combines IVF indexes with RaBitQ quantization to deliver Pinecone-class performance at billion-vector scale while keeping all data inside a single Postgres database — no separate vector store, no two-system sync, no rewrites when the workload grows.

Fast embeddable vector search engine

USearch is a high-performance vector search engine implementing HNSW algorithms for approximate nearest neighbor queries across C++, Python, JavaScript, Rust, Java, Go, and more. It supports user-defined distance metrics, memory-mapped persistence for datasets larger than RAM, and filtered search with predicates. Used by YugabyteDB and ScyllaDB as their production vector indexing backend.

In-process vector database — the SQLite of vector DBs

Zvec is an open-source in-process vector database from Alibaba designed as the SQLite of vector search. It runs as an embedded library directly inside applications without requiring external servers, delivering 8,000+ QPS with high recall rates. Zvec supports dense and sparse embeddings, multi-vector queries, and combined semantic plus structured filtering. Built on Alibaba's proven Proxima engine, it provides a lightweight alternative to server-based vector databases for local AI workflows.