MRPT (Multi-Resolution Proximity Trees) is an open-source library for fast approximate nearest neighbor search in high-dimensional vector spaces, applicable to vector database backends.

ClickHouse is a columnar OLAP database with vector indexes (ANN via AMM, brute-force), supporting SQL queries over vectors + structured data at petabyte scale. Excels in aggregations with vectors. For analytics workloads with embeddings; faster ingestion than Postgres pgvector for big data.

NGT (Neighborhood Graph and Tree) is an open-source vector search engine designed for fast and scalable approximate nearest neighbor search.

Puck is an open-source vector search engine designed for fast similarity search and retrieval of embedding vectors.

Rust library for low-latency on-device vector similarity search using random projection trees and LMDB storage, enabling efficient ANN on edge devices. Supports concurrent multi-process access for real-time AI apps. Ideal for IoT and embedded systems vs cloud alternatives like Qdrant.

Havenask is an open-source, self-hosted distributed search engine from Alibaba with vector search for large-scale AI applications. Key features include high QPS/TPS, millisecond latency, SQL queries, and free use. Suited for production RAG and search, self-hosted for cost efficiency vs managed like Pinecone.