head to head · open source
haystack vs flowable-engine
haystack has 26,924 GitHub stars, 3,388 forks, 143 open issues and last shipped yesterday. flowable-engine has 9,635 stars, 2,904 forks, 411 open issues and last shipped 18 days ago. haystack leads on adoption by 179% (26,924 vs 9,635 stars). haystack is written in Python under Apache-2.0; flowable-engine is written in Java under Apache-2.0. haystack has attracted 13% as many forks as stars, flowable-engine 30%. haystack was the more recently maintained of the two, and both are self-hostable with no licence fee.
Two open source projects, one decision. Both are free and self-hostable — the differences are community size, license terms, language stack and release pace.
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Side by side
| haystack | flowable-engine | |
|---|---|---|
| GitHub stars | ★ 27K | ★ 9.6K |
| License | Apache-2.0 | Apache-2.0 |
| Written in | Python | Java |
| Last push | 2026-11-04 | 2026-10-18 |
| Forks | ⑂ 3.4K | ⑂ 2.9K |
| Self-hosting | Yes | Yes |
| Data ownership | Your server | Your server |
pick haystack if
- You weight community size — 27K stars and counting
- You want the Apache-2.0 license terms
- Your stack matches Python
- You value the larger contributor base for long-term maintenance
pick flowable-engine if
- You want the flowable-engine feature set and don't need the biggest community
- You prefer the Apache-2.0 license terms
- Your stack matches Java
- You evaluated both and flowable-engine fits your workflow better
About haystack
🎉🎊✨ Haystack 3.0 is out! ✨🎊🎉 Read the announcement here! 🥳 🎈 🎆 🪅 🎇 🍾 🥂 🎁 🌈 Haystack is an open source AI orchestration framework for building production ready LLM applications in Python. Design modular pipelines and agent workflows with explicit control over retrieval, routing, memory, and generation. Build scalable RAG systems, multimodal applications, semantic search, question answering, and autonomous agents, all in a transparent architecture that lets you experiment, customize deeply, and deploy with confidence. Table of Contents Installation Documentation Features Haystack Enterprise: Support &…
read the full haystack overview →
About flowable-engine
Flowable ======== Homepage: flowable / flowəb(ə)l / a compact and highly efficient workflow and Business Process Management (BPM) platform for developers, system admins and business users. a lightning fast, tried and tested BPMN process engine, CMMN case engine and DMN rule engine written in Java. It is Apache 2.0 licensed open source, with a committed community. can run embedded in a Java application, or as a service on a server, a cluster, and in the cloud. It integrates perfectly with Spring. With a rich Java and REST API, it is the ideal engine for orchestrating human or system activities. Introduction…
read the full flowable-engine overview →
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Frequently asked questions
Is haystack or flowable-engine more popular?
haystack has 26,924 GitHub stars and flowable-engine has 9,635. haystack has the larger community by that measure.
Are haystack and flowable-engine free?
Both are open source. haystack is licensed under Apache-2.0 and flowable-engine under Apache-2.0. Neither carries a licence fee.
What is the difference between haystack and flowable-engine?
haystack is written in Python and flowable-engine in Java. The practical differences are community size, licence terms, language stack and release cadence — all compared in the table above.
Which should I choose, haystack or flowable-engine?
Choose haystack if you want the larger community (26,924 stars) or its Apache-2.0 licence terms. Choose flowable-engine if its feature set, stack or Apache-2.0 licence fits better. Both are self-hostable.