Vespa

Vespa is an open-source AI search platform and vector database that unifies vector, lexical, and structured search with advanced ranking in a single query, built for large-scale, real-time production systems.

Vespa is a mature, open-source platform for building applications that need fast and accurate search, personalized recommendations, and real-time data serving over large, continuously updated datasets. Originating from technology used at web scale, it is a fully featured search engine and vector database that can combine vector similarity (ANN), traditional lexical search, and filtering over structured data all within the same query, which is a strong fit for hybrid retrieval and advanced RAG. Unlike vector-only databases, Vespa is designed for complex ranking and serving workloads: it supports custom ranking expressions, machine-learned ranking models, and real-time indexing at scale, making it suitable for large production systems that go beyond simple nearest-neighbor lookups. It is open source under the Apache 2.0 license, so teams can download and self-host it. For teams that prefer not to operate it themselves, Vespa Cloud provides a managed, serverless deployment at cloud.vespa.ai, with a free trial to get started. Vespa's combination of hybrid search, sophisticated ranking, and proven scale makes it a compelling choice for organizations building demanding search and recommendation systems, though its power comes with a steeper learning curve than lighter-weight vector databases.