Founding Fullstack Engineer @Rose

Paris
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

  • 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

  • AI & Performance

  • 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

  • Integrations & Product

  • 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
Publié le 2025-11-15

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