Glossary · AI & Agents
Haystack
Overview
What Haystack is
Haystack is an open-source Python framework, maintained by the company deepset, for building applications powered by large language models. It is best known for retrieval-augmented generation and semantic search, where an app retrieves relevant documents and uses an LLM to answer questions grounded in that content. It supports document stores, embedding models, retrievers, and generators as composable building blocks.
How pipelines work
Haystack organizes work into pipelines: graphs of components that pass data from one step to the next. A typical RAG pipeline embeds a query, retrieves matching chunks from a vector database, and feeds them to an LLM to generate a cited answer. Components are swappable, so teams can change models or databases without rewriting the app, and pipelines can branch for complex logic.
Why it matters for a business
Haystack lets a team build a knowledge assistant that answers from a company's own documents instead of guessing, reducing hallucinations and support load. Because it is open-source and vendor-neutral, projects avoid lock-in to a single model or database. A full-service team uses Haystack in RAG development and knowledge-assistant work to turn internal content into reliable, searchable answers.
Where we use it
Related Zen in Tech services
How our team puts Haystack to work in real projects.
FAQ
Haystack — common questions
What is Haystack used for?
Haystack is used to build LLM applications like retrieval-augmented generation, semantic search, question answering, and document-based chatbots. It connects models, retrievers, and vector databases into pipelines that answer questions from your own data.
Haystack vs LangChain: which should I use?
Both are frameworks for LLM apps. Haystack is Python-focused and search-first, with a clean pipeline model favored for production RAG and question answering, while LangChain has a broader, faster-moving ecosystem and more integrations. The right pick depends on your stack and team preferences.
Is Haystack free?
Yes. Haystack is open-source and free to use under a permissive license. You pay only for the infrastructure and model or embedding APIs you run it with. deepset also offers commercial platforms built on top of it.
Need Haystack done right?
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