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Valentin MantezVM

Valentin Mantez

Full-Stack Developer & System Integration

€320/day
Lille, FR
0-2 years

Average response time: 1 hour

Freelancer profile translated to English.
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About Valentin

Hi, I'm Valentin 👋

I help companies design web applications, business tools, and simple, reliable integrations tailored to their real needs.

My goal is to support you on concrete projects: creating a web interface, connecting tools to each other, structuring data, documenting an API, improving an internal process, or developing a clean prototype to test an idea quickly.

With 3 years of experience in system integration, web services, SQL, API documentation, and coordination between business and technical teams, I've learned not just to "code a request," but to understand the need behind the request.

I can help with:
  • Full-stack web application development
  • Creation of internal tools or business interfaces
  • API / web service integration
  • SQL data manipulation and structuring
  • Technical and functional documentation
  • Support for scoping digital needs
  • SaaS prototypes, MVPs, or demonstration tools
My profile aligns with a Product Engineer approach: I like to understand the context, exchange with users, propose a realistic solution, and then develop it properly until it's usable.

I primarily work with technologies like JavaScript, TypeScript, React, Next.js, Node.js, SQL, as well as API integration and documentation environments.

What I can bring you: a serious, clear, and pragmatic approach, with a real focus on understanding business needs, the quality of the deliverable, and ease of use.

Available for remote or on-site missions in Hauts-de-France, particularly around Lille, Valenciennes, Douai, and Saint-Amand-les-Eaux.

Looking forward to discussing your project!
  • French

    Native or bilingual

  • English

    Fluent

Can work on-site
Lille (up to 50km), Valenciennes (up to 30km), Orchies (up to 30km)

Experience

  • VM Solution
    Founder / Full-Stack Developer & IT Consultant
    SOFTWARE PUBLISHING
    May 2026 - Today (1 month)
    Lille, France
    I support SMEs, freelancers, and business teams in designing web tools, automating processes, and integrating simple, reliable, and maintainable digital solutions.

    Services offered:
    • Design of business web applications
    • Process automation and reporting
    • API integration and data synchronization
    • Creation of dashboards and internal tools
    • Technical scoping and project support: helping SMEs, freelancers, and business teams transform concrete needs into simple, maintainable, and efficient digital solutions.
    Development of a web solution project focused on accessible music creation, supported within an incubation program. Work on product vision, prototyping, UX, user validation, and business model.
    Web Development Business Process Automation Project Management API Integration
  • SERGIC
    Apprenticeship: Project Manager Assistant / SI Integration Developer
    REAL ESTATE
    August 2022 - August 2025 (3 years)
    Wasquehal, France
    For 3 years at SERGIC INVEST, I worked on integrating webMethods into the existing information system, with the goal of automating, ensuring reliability, and structuring data exchange between the company's various tools.

    My role involved designing, developing, and maintaining services to connect applications, process business data, and expose or consume APIs. I specifically worked on flows related to databases, web services, exchanges with internal/external solutions, and interface documentation.

    This experience allowed me to work on both technical and functional aspects: understanding business needs, analyzing existing flows, designing suitable solutions, writing API documentation, testing, bug tracking, and progressively improving production processes.

    I contributed to:
    • webMethods integration into the existing IS
    • Design and development of integration services
    • Creation and documentation of REST web services
    • Manipulation and exploitation of SQL data
    • Structuring flows between internal and external applications
    • Writing Swagger / OpenAPI documentation
    • Collaboration with business teams to translate needs into technical solutions
    • Improving the reliability, readability, and maintainability of production flows
    This experience gave me a real insight into the challenges of an enterprise IS: data quality, reliable exchanges, clear documentation, business understanding, and the ability to deliver useful solutions within an existing environment.

    Technical environment: webMethods, API Gateway, IBM Integration Server, REST, OAuth2, Swagger, OpenAPI, Java, Angular, Vue.js, Node.js, SQL, AS400, SAGE, Bluesoft, Microsoft Azure
    Webmethods GitHub Project Management AngularJS Java
  • MUSICRAFT
    Founder / Product Builder
    CULTURE
    April 2026 - Today (2 months)
    Roubaix, France
    Musicraft is a web software project aimed at making music creation more accessible to beginners, particularly in educational, associative, and cultural contexts.

    The idea is to offer an experience inspired by visual creation tools: allowing a user to quickly compose music using sound blocks, without needing to master music theory, an instrument, or complex music production software.

    On this project, I work on product design, user experience, interface prototyping, and exploring real-world use cases: students, teachers, cultural organizations, associations, or beginners wanting to explore music composition.

    I am studying:
    • Definition of the concept and value proposition
    • Design of a simple, progressive, and pedagogical user experience
    • Creation of web interface prototypes
    • Exploring uses in educational and cultural settings
    • Integration of learning and progression mechanics
    • Development of a prototype combining music, digital technology, and pedagogy
    • Preparation of materials to present the project to teachers, partners, and support organizations
    This project allows me to develop a comprehensive approach, close to a Product Engineer: understanding user needs, structuring a solution, designing a clear interface, prototyping quickly, and transforming an idea into a testable product.

    Musicraft has also been part of an incubation program, which allowed me to confront the project with positioning, field validation, and product development challenges.

    Environment / Skills used:product design, UX/UI, web prototyping, React, Next.js, TypeScript, Tailwind CSS, music pedagogy, MusicTech, EdTech, MVP.
    Wireframing Project Management React.js Computer Music autonomy

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Education

  • Master I2l, Computer Science
    Université du Littoral Côte d'Opale
    2025
    Master I2l, Informatique
  • Professional Bachelor's Degree, Computer Science
    Iut de Calais
    2023
    Licence professionnelle, Informatique

Skill set

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