Apache Cassandra is a distributed NoSQL database that is adding native support for high-dimensional vector storage and approximate nearest neighbor search, making it a scalable choice for AI and vector search workloads.

Elasticsearch is a distributed search engine supporting various data types, including vectors, and provides scalable vector search capabilities, making it a popular choice for modern AI-powered applications. It can be extended with the k-NN plugin to provide scalable vector search using HNSW and Lucene, enabling hybrid semantic and keyword search capabilities.

Milvus is a mature, open-source vector database maintained by Zilliz, supporting large-scale similarity search with multiple indexing strategies and GPU acceleration. It includes variants such as Milvus Lite (lightweight version), Milvus Standalone (single-machine deployment), and Milvus Distributed (Kubernetes-based deployment for large scale).

OpenSearch is a fully open-source, community-driven search and analytics suite that supports vector search, providing a transparent and flexible alternative for organizations seeking advanced search features.

Vald is an open-source, highly scalable distributed vector search engine known for its asynchronous auto-indexing and ability to efficiently handle large-scale vector data in real time, making it suitable for demanding vector search applications.

Vearch is a distributed vector search engine designed for AI-native applications, enabling scalable and efficient similarity search across large datasets.