Founding Fullstack Engineer Rose
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Job Location:
Monthly Salary:
Posted on:
30-10-2025
Vacancies:
1 Vacancy
Job Summary
Hexa
Rose is a startup launched by Hexa the Paris-based startup studio founded in 2011 that has created over 40 companies including Front Aircall Spendesk and Swan (3 unicorns $700M raised portfolio valuation >$5B).
With 29M in funding finalized in 2025 and the goal to launch 30 startups per year by 2030 Hexa offers a unique environment: shared resources expert network and an ecosystem of hundreds of engineers and founders.
Rose in a nutshell
The problem: 85% of B2B website visitors leave without interaction. Meanwhile they use ChatGPT and Perplexity to compare solutions before even contacting you.
Our mission: Transform B2B websites into intelligent conversational assistants that engage 100% of traffic capture quality zero-party data and increase demo conversions.
Our approach: Unlike traditional chatbots (5% engagement) Rose achieves 20% engagement through an integrated assistant experience not an intrusive popup.
Our clients: Pennylane Mayday AB Tasty are already using Rose in production.
The role
Youll join Rose as the first Founding Engineer to build the platform alongside Benoit CTO/Cofounder.
Youll work on cutting-edge technical challenges in an environment where every line of code has a direct impact on the product and users.
Your missions
- Architecture & Development
- AI & Performance
- Integrations & Product
Co-build the technical architecture with the CTO (backend frontend infrastructure)
Develop core features: conversational AI engine interactive experiences third-party integrations back-office
Make technical choices that structure the platform for the next 5 years
Participate to the implementation of RAG (Retrieval-Augmented Generation) systems in production with Vector database and knowledge graph
Optimize real-time performance
Develop guardrails and testing mechanisms to ensure AI response quality
Build bidirectional integrations with CRMs (Salesforce HubSpot)
Orchestrate calendar systems (Calendly Chili Piper) and analytics (Posthog)
Participate in product decisions and user exchanges
Tech Stack
- Backend: Python Fast API PostgreSQL MongoDB Vector Database Neo4j
- Frontend: React TypeScript AI/ML: LLMs Vector embeddings prompt engineering Langgraph
- Infrastructure: GCP GitHub Actions monitoring and observability
Tech Philosophy
- We favor pragmatism over theoretical perfection iteration velocity over over-engineered architectures and user impact over technical elegance. Youll work in an environment where we ship quickly test with real users every week and learn constantly.
Who were looking for
- 4 years of experience in fullstack development on B2B SaaS products
- Mastery of React/TypeScript on the frontend and a modern backend framework
- Experience with Python
- Experience with SQL and NoSQL databases REST or GraphQL API design
- Ability to define technical architectures and challenge design decisions
- Experience deploying and monitoring applications in production
Mindset
- Builder first: you prefer building and iterating rather than debating for hours
- Product-minded: you think about user impact before technical elegance
- Ownership: you make decisions own the results and adjust
- Adaptability: youre comfortable with ambiguity and pivots of an early-stage startup
- Technical curiosity: you love learning (generative AI for example even if youre a beginner)
Nice to have
- UX and design sensibility
- Experience with complex third-party integrations (CRM analytics calendars)
- Experience with generative AI or LLMs
- International or multilingual context
What we offer
- Competitive salary aligned with the senior engineer market in Paris
- Lastest Macbook Pro
- Premium health insurance (Alan or equivalent)
- Joining a renowned startup studio: youll be in a dynamic environment surrounded by smart and ambitious people in a fun atmosphere
- Lovely offices at Hexa in Paris (75010)
- Hybrid remote: 2 days a week in the office the rest is up to you
Recruitment process
We respect your time with an efficient 3 week process:
- Discovery HR interview (30 min) - Rose presentation discussion about your background
- CTO interview (45min) with the CTO - Discussion about your experiences technical approaches
- Tech assessment (2-3h max) - Realistic technical problem related to our challenges (remote possible)
- Final meeting (2h) at the office - Technical deep dive culture fit with Johary CEO & Florent Partner Hexa
- References and formal offer
Key Skills
- ASP.NET
- Health Education
- Fashion Designing
- Fiber
- Investigation
About Company
Hexa is home to startup studios eFounders, Logic Founders and 3founders. We’re on a mission to democratize a new way for entrepreneurship.
