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

Emplois Recommandés

Attaché ommercial Tourisme H/F

Page Personnel
Paris 2e

À propos de notre client: Qu'il s'agisse d'un séjour culturel , d'une escapade romantique , d'une aventure hors des sentiers battus , d'une parenthèse au bout du monde ou d'un voyage fami…

Voir les Détails
Publié le 2026-01-09

Responsable de projets techniques Espace Client B2B (h/f)

SFR
Paris

Description de l'offre ·  Date de publication : 29/09/2025 ·  Type de contrat : CDI ·  Département : Paris (75) ·  Ville : PARIS Informations générales Entreprise d'innovation et 2ᵉ opé…

Voir les Détails
Publié le 2025-11-29

Chef de Projet Informatique - Mutuelle Française (H/F)

Silkhom
Paris

En bref Paris CDI 12/12/2025 50000€ - 55000€ Société Notre client est un acteur majeur de la protection sociale et de la santé, fondé en 1902. Il fédère aujourd’hui la quasi-totalité de…

Voir les Détails
Publié le 2025-12-12

Data Science Intern

Louis Vuitton
Paris

Louis Vuitton seeks a Data Science Intern to join its Paris office, working full-time for six months starting April 2026. The role involves developing machine learning models, supporting CRM and Retai…

Voir les Détails
Publié le 2025-12-12

Alternance - Accompagnateur(trice) de Voyage - BTS Tourisme

Aurlom BTS+
Paris

Cette opportunité s'adresse aux étudiants(e) souhaitant préparer un BTS TOURISME à la rentrée 2026 à l'école Aurlom. Bienvenue chez Aurlom BTS+ ! Nous sommes une école spécialisée dans la prépara…

Voir les Détails
Publié le 2026-01-09

Tech Lead Devops - expert Ansible

Paris

Rejoignez notre équipe qui intervient, dans le secteur bancaire, en tant que Consultant spécialisé en automatisation. Vos responsabilités principales incluront : Gestion et maintenance de la pla…

Voir les Détails
Publié le 2025-12-06

Assistant-e de Direction - Administration, Comptabilité & Dossier (H/F)

EXPERT DE LA RENOVATION ENERGETIQUE DU B
Paris

Qui sommes-nous ?EREB ÉNERGIE accompagne particuliers et petits professionnels dans la rénovation énergétique (isolation, PAC, photovoltaïque) et prend en charge le financement via MaPrimeRénov' et l…

Voir les Détails
Publié le 2026-01-12

AIDE SOIGNANT(E) H/F - CARDIOLOGIE - PARIS 14

Ergalis Médical Paris
Paris 14e

A propos de Ergalis Médical Paris: Notre cabinet ERGALIS MEDICAL, propose des solutions adaptées aux établissements sanitaires et sociaux pour le recrutement et de la fidélisation du personnel en VAC…

Voir les Détails
Publié le 2025-12-26

Business Development Specialist S3P F/H

Bodycote
Paris

About Bodycote At Bodycote, we’re more than the world’s leading provider of heat treatment and specialist thermal processing services, we’re a people business at heart. Our commitment to innovat…

Voir les Détails
Publié le 2025-11-28