Open-Source Hybrid Keyword and Semantic Search Engines
OpenSearch (Elasticsearch Open Source Fork) • Ease of Setup & Scalability: OpenSearch is a drop-in replacement for Elasticsearch, offering easy cluster deployment via Docker or managed services. It’s built on Lucene, so it scales horizontally and handles large indexes reliably. Unlike Elasticsearch’s basic tier, OpenSearch has no license restrictions on advanced features , making it fully open-source and cost-free to scale out. • Semantic Search Flexibility: OpenSearch supports dense vector fields (knn_vector) for embeddings and can execute kNN (nearest neighbor) searches natively . It enables hybrid search: you can combine traditional BM25 keyword matches with semantic vector similarity in one query . For example, a query can have both a full-text component and an embedding-based component, with their scores fused. It also provides a Neural Search plugin to automate embeddings – you can configure a transformer model in an ingest pipeline to generat