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Marvin FrachetMF

Marvin Frachet

Fullstack Engineer

€900/day
Strasbourg, FR
8-15 years

Average response time: 1 hour

Freelancer profile translated to English.
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About Marvin

Build fast, yes. Build fragile, no.

Early-stage startups need to move fast: test an idea, launch a first version, integrate AI, automate a business process, create a SaaS, a copilot, or a new product experience.

But going fast shouldn't mean piling up hard-to-maintain code, creating a prototype that's impossible to evolve, or throwing everything away when it's time to go to production.

That's where I come in.

I help you quickly build web, mobile, or AI products with solid foundations: clear architecture, maintainable frontend, polished user experience, performance, accessibility, testing, and scalability.

The goal is simple: enable you to move fast without creating technical debt that will slow you down in three months.

I am a freelance Staff Frontend Engineer with 13 years of experience in React, React Native, TypeScript, and modern JavaScript. I've contributed to products like Gatsby, Strapi, OpenClassrooms, M6, Zealy, and Mastra, as well as platforms used at scale.

Today, I'm working on Mastra, an open-source TypeScript framework for building agentic applications with agents, tools, memory, and workflows. This experience allows me to help teams that want to integrate AI into a real product, not just a fragile demo.

I don't just "code screens." I help transform an idea into a usable, robust, and scalable product: technical choices, frontend architecture, design system, developer experience, testing automation, accessibility, performance, AI, web, or mobile.

An MVP, yes. A disposable toy, no.
  • French

    Native or bilingual

  • English

    Fluent

Can work on-site
Strasbourg (up to 20km)

Experience

  • Mastra
    Senior Product Developer
    TECH
    March 2025 - Today (1 year and 3 months)
    Strasbourg, France
    Frontend lead and core contributor at Mastra, an open-source TypeScript framework for building AI applications with 20k+ GitHub stars.

    I lead the development of Mastra Studio, the product interface used to build, inspect, and manage AI agents. I also contribute heavily to the Mastra PaaS platform, the hosted product that turns the open-source framework into a monetizable SaaS offering by allowing companies to deploy and run Mastra applications at scale.

    My current focus is the Agent Builder, an AI-powered enterprise feature that helps users create and configure agents more efficiently. This feature is part of Mastra’s Enterprise Edition and contributes directly to the company’s revenue strategy.

    This work places me at the intersection of developer experience, AI application infrastructure, frontend architecture, and revenue-generating SaaS product development.
    Typescript Node.js React.js Artificial Intelligence Next.js
  • Zealy
    Senior Software Engineer
    SOCIAL NETWORKS
    April 2024 - March 2025 (11 months)
    Strasbourg, France
    Full-stack contributor with hands-on experience building AI-powered products and community engagement platforms.

    I worked on several AI experiments using the Vercel AI SDK, React, and the broader TypeScript ecosystem. One project focused on training a model to recognize a user’s tone of voice on social media, then help them generate high-performing tweets while preserving their own personal writing style.

    I also experimented with LlamaIndex and early retrieval-based systems to connect external data sources to AI interfaces, before MCP became widely adopted. The goal was to let users interact with structured and unstructured data through a conversational chat experience.

    Alongside this AI work, I contributed to Zealy.io across both frontend and backend. Zealy is a platform that helps companies and communities drive engagement by creating quests, events, and reward-based participation systems.

    I worked on several product features, including a time-based quest and feed experience, where users had to complete a set of tasks within a limited timeframe. Community members could then vote for their favorite submissions, with winners earning rewards such as gifts, crypto, or community points.
    Typescript Artificial Intelligence React.js Next.js Node.js
  • Proton | Privacy by Default
    Senior frontend engineer
    TECH
    October 2022 - March 2024 (1 year and 5 months)
    Strasbourg, France
    Frontend engineer responsible for building and scaling high-traffic marketing websites using Gatsby, Astro, and React.

    I worked on the company’s marketing websites, building performant, SEO-friendly static experiences on top of Gatsby, Astro, and the React ecosystem.

    The platform generated around 15,000 static pages, designed to support large-scale content distribution, search visibility, and fast page loading across a wide range of markets and audiences.

    These websites reached approximately 2 billion people per year, making performance, reliability, accessibility, and maintainability critical parts of the work.
    React.js Typescript Node.js Astro Gatsby

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Education

  • L3 Degree DASI (Information System Development and Administration), Management Information Systems
    Information Systems Management
    2013
    Licence L3 DASI (Développement et Administration de Système d'Information), Systèmes
  • General and Technological High School Carriat BTS, Management Information Technology
    Joseph Fourier University
    2012
    Lycée général et technologique Carriat BTS, Informatique de gestion

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