The Role
Join as the first Founding Engineer to develop an intelligent conversational platform for B2B sites, focusing on architecture, AI, and integrations.
Summary Generated by Built In
🚀 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
You'll join Rose as the first Founding Engineer to build the platform alongside, Benoit, CTO/Cofounder.
You'll 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. You'll work in an environment where we ship quickly, test with real users every week, and learn constantly.
👤 Who we're 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: you're comfortable with ambiguity and pivots of an early-stage startup
- Technical curiosity: you love learning (generative AI, for example, even if you're 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: you’ll 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
Top Skills
Fast Api
GCP
Github Actions
MongoDB
Neo4J
Postgres
Python
React
Typescript
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The Company
What We Do
Hexa is a startup studio.
It all started in 2011 with startup studio eFounders, which pioneered a new way of entrepreneurship, became a reference in the B2B SaaS world, and launched over 50 companies including 3 unicorns (Front, Aircall, Spendesk).
In 2022, eFounders became Hexa, to scale our ambitions further and launch startups in new verticals: AI, web3, fintech, future of work, health.
With Hexa, we’re on a mission to democratize a new way for entrepreneurship, one centered around building companies in teams.
In numbers? We’re an entrepreneurial ecosystem made up of:
- +40 companies launched
- +2800 jobs created
- 3 unicorns (Spendesk, Aircall, Front)
- +$4.5 billion combined companies valuation
