Senior Developer - LuCE Chatbot (Freelance)
Digital nomads. Work from anywhereCompany: Lung Cancer Europe
Who We Are
Lung Cancer Europe is the European umbrella organisation representing people affected by lung cancer. We work across Europe to improve access to care and connect patients and caregivers with the information they need.
The Project
We are building the Lung Cancer Europe Chatbot — a RAG-based AI assistant giving lung cancer patients and caregivers access to validated health information across multiple European languages. The knowledge base is clinically validated and shaped in collaboration with our Patient & Caregiver Board and Scientific & Clinical Board.
The chatbot is an information tool, not a medical device. It will run on open-weight models on European infrastructure, GDPR and EU AI Act compliant from day one.
The Role
A focused freelance engagement, fully remote. The core build is planned for July (5 days / 40 hours), followed by availability for support and troubleshooting through to our official launch in December.
You will work closely with the project lead, who also has developer experience and will maintain the system after handover. How you document and explain decisions matters as much as what you build. System prompts will be developed collaboratively with our steering committee. Follow-on feature work is likely beyond December.
Key Responsibilities
* Design the full RAG pipeline: ingestion, chunking, vector storage, retrieval, and LLM inference
* Select and configure servers, with clear justification for each decision
* Design for scalability, including usage peaks (e.g. conferences)
* Design folder structure, metadata, and update workflows the in-house team can operate without developer support — LuCE supplies the documents, you determine how they are parsed and stored
* Ensure GDPR compliance, EU AI Act compliance, and that the system does not constitute a medical device
* Produce complete technical documentation and participate in a structured handover
What We Are Looking For
Essential
* Proven experience architecting RAG-based chatbot systems
* Experience deploying open-weight models
* Strong grasp of vector databases, embeddings, and chunking strategies
* Able to document and hand over to a mid-level developer
* GDPR knowledge as it applies to hosted AI systems
* Fluent English
A plus
* FlowiseAI or similar RAG tooling experience
* Medical or health data experience
* EU AI Act familiarity
* Multilingual NLP experience
How to Apply
Please send your CV and an architectural proposal to melanie.decoster@lungcancereurope.eu. The proposal should be substantive enough for us to assess your technical approach. Please address the following:
Model selection
Which open-weight model would you recommend for this use case and why? We are currently leaning toward open-weight models for compliance and cost reasons, but we are genuinely open to other approaches — including proprietary models — and interested in your reasoning.
Knowledge base structure
How would you organise the knowledge base? Address folder structure, pathology separation, metadata strategy, and chunking approach. Bear in mind the lung cancer field changes rapidly and the system must handle documents ranging from short FAQ sets to 500-page clinical assessment reports.
Document updates
How would document updates and additions work in practice — without requiring developer intervention each time? The scientific board needs to be able to add, remove, and flag outdated content independently.
Scalability
How would you design for usage peaks, for example during a major European oncology conference?
GDPR and EU-server hosting
How would you ensure all data stays on European infrastructure, and what does your compliance approach look like in practice?
RAG orchestration tooling
What tooling would you recommend and why? We have looked at FlowiseAI but are open to alternatives.
Not a medical device
How would you ensure the system does not cross into medical device territory, and how would you document that for regulatory purposes?
Contract Details
Type: Freelance / Independent Contractor
Location: Remote
Timeline: Core build July 2026; support availability August–December 2026
Compensation
Project fee for the core build, paid in milestones:
* 25% on architecture sign-off
* 50% on working prototype
* 25% on completed handover
Support retainer August–December 2026.
Budget available on request.
Applications are reviewed on a rolling basis.