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Guillaume G.GG

Guillaume G.

Backend & Business Automation Developer

€500/day
4 projects
Paris, FR
8-15 years

Average response time: 1 hour

Freelancer profile translated to English.
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About Guillaume

Automation, Secure API Architectures & TDD

Launching, automating, or making a web project more reliable? I support you as a technical partner with a pragmatic, results-oriented approach focused on clarity and efficiency.

My goal: To translate your business challenges into concrete, ultra-performant, and automated architectures, without ever sacrificing security or long-term vision.

🚀 My Pillars of Intervention

Automation & TDD: Design of workflows and scripts (PHP/Python) fully covered by tests. Test-Driven Development is my guarantee of robustness for smooth deployments without regressions.

API Ecosystem & Tooling: Design of highly connected RESTful and GraphQL APIs. Mastery of modern stacks (CI/CD, Docker, monitoring).

Cyber Mindset (Security by Design): Your data flows are critical. I integrate the strictest security standards (OWASP, fine-grained authorization management, encryption) from the very first line of code.

Business Alignment & Management: With a hybrid profile (tech + project management), I communicate directly with your teams or clients to streamline delivery (specifications, agility, coordination).

🛠️ Technical Expertise & Methodologies

Developer for over 10 years (Start-ups, SMEs, Large Corporations), I shape clean, modular, and scalable architectures:

Back-end & Automation: PHP (Symfony — my preferred framework, Laravel, Phalcon), Python (automation, scripting, data).

Front-end & Fullstack: Modern ecosystems including Node.js, TypeScript, React/Next.js, and Vue/Nuxt.js for fluid interfaces.

Craftsmanship & Architecture: Hexagonal Architecture, DDD (Domain-Driven Design), TDD, API-first, SecOps, and rigorous documentation.

My method is simple: solid, tested, highly secure code, and clear communication at every step. Let's discuss your project!
  • French

    Native or bilingual

  • English

    Fluent

  • Spanish

    Fluent

Can work on-site
Paris (up to 50km)

Experience

  • Techne-Lab
    Backend & Technical Lead Developer
    DIGITAL AND IT
    December 2024 - Today (1 year and 6 months)
    Paris, France

    Techne Lab — IT Agency dedicated to the digital transformation of VSEs

    • **Automation & TDD**: Design and automation of complex business workflows through a rigorous test-driven approach (TDD), ensuring code robustness and maintainability.
    • API Architecture & Tooling: Modeling and development of robust RESTful APIs (Symfony), interconnected with a modern ecosystem of tools (CI/CD, Docker, monitoring tools) and Python automation scripts.
    • Cyber Mindset & Security by Design: Native integration of security best practices (OWASP, fine-grained authorization management, encryption) to secure data flows and automations.

    Business Projects & Achievements:

    • Development of complex applications: Design and development of a custom Web application (Symfony) for an accounting firm, streamlining and automating client interactions.
    • SecOps & Data Transfer: Implementation of a highly secure system for transferring and storing sensitive accounting documents.
    • Planning & Business Logic: Integration and synchronization of calendar software via API for automation and planning of accounting exercises.
    • Co-design & Business Approach: Direct collaboration with clients to translate their business processes into technical specifications and design software architectures perfectly aligned with their needs.
    Symfony Project Management Cybersecurity Automation AI Agent
  • Obat
    Symfony Back-end Developer
    CIVIL ENGINEERING
    June 2024 - December 2024 (6 months)
    Paris, France
    Obatis an innovative startup offering invoicing management solutions for construction companies.

    As a member of the "Cash" team, I participated in the development and optimization of tools related to accounting and invoicing:

    Main Missions

    Transfer of accounting data to Pennylanevia theCHIFTAPI:
    • Optimization of exchanges with a Symfony response streaming solution.
    • Advanced management of accounting flows, allowing me to deepen my mastery of accounting management.

    **Advanced user features**:
    • Addition of tools allowing users to view costs and profitability per construction site.
    • Multi-user management with specific roles: accountant, site manager, president, etc.

    Architecture and quality

    • Implementation of a hexagonal architecture on a PHP Symfony 6 and 7 base, with a multi-service breakdown.
    • Adherence to a code coverage of at least 80%, checked with tools like Deptrac, PHPStan, and SonarCloud.
    **Strict contracts**:
    • Contractual API between back and front, validated by contract tests.
    • Internal contracts between backend services, ensuring the robustness of exchanges.

    Results and impact

    • Significant improvement in the performance and reliability of accounting data transfer.
    • Enrichment of features for users, facilitating their business management and decision-making.
    • Implementation of processes and tools guaranteeing code quality and long-term maintainability.
    PHP Symfony React.js
  • EISF - EDLP
    Tech Lead
    EDUCATION AND E-LEARNING
    September 2023 - Today (2 years and 9 months)
    Paris, France
    L’EISF and EDLPare organizations offering distance learning:

    - EISF specializes in CAP diplomas highlighting French know-how (pastry chef, baker, chocolatier).
    - EDLP offers training in photography, marketing, and web professions.

    As **Project Manager**, I supervised the technical management and evolution of both platforms:

    Migrations and infrastructure:

    - Migration ofSymfonyenvironments (2.3 → 6.4): rewriting key modules withautomated teststo prevent regressions.
    - Server modernization (**Debian** 8 → 11) and implementation ofPleskfor simplified infrastructure management.

    Automation and optimization:

    - Optimization of thesales funnelto improve user experience.
    - Automation of subscription payments withDalenysand **Payplug**.
    - Implementation of automated management ofuser rightsand training access.
    - Automatic invoice generation with **Payum Be2Bill**, eliminating manual interventions.

    Integration and unification

    - Unification of the two platforms via aFactory (Design Pattern)for centralized maintenance.
    - Integration ofHubSpotfor effective CRM management and lead tracking.

    Quality Guarantees

    - Implementation ofquality control tools(PHPStan, SonarQube) to ensure robust code.
    - Use ofunit and functional tests(PHPUnit) and integration tests to validate each delivery.
    - Automation of deployments withCI/CDpipelines and environment standardization via **Docker**.

    This experience highlights my skills in managing complex technical projects, optimizing processes, and ensuring quality in demanding environments.
    Symfony PHP

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Education

  • Expert in Information Technology
    Epitech Paris
    2017
    Epitech est une école d'informatique suivant un cursus en 5 ans. Elle a pour vocation de former des experts en informatique, des innovateurs, de vrais dirigeants capables d’imaginer et de créer le futur de l’informatique et le meilleur de l’innovation. Grâce à une méthode pédagogique centrée sur le concret, les étudiants acquièrent des connaissances et des compétences en réalisant de nombreux projets, généralement en groupe. La formation permet d’accéder à des postes à responsabilités en France comme à l’international dans tous les secteurs de l’économie et dans tous les domaines technologiques comme la sécurité informatique, le big data, l’embarqué, l’intelligence artificielle.

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