Freelancer profile translated to English.
Back to original languageAbout Guillaume
Looking for a senior fullstack developer to design / evolve a SaaS platform, a business tool, or a custom web application?
I support my clients on high-stakes product projects, from architecture to development, with a particular focus on robustness, performance, and user experience.
For me, web development is a modern craft: assembling technical components to create useful, robust, and elegant products. I enjoy starting from a concrete need, structuring a clear solution, and then making it tangible through intuitive interfaces and a sound technical foundation.
What I can bring:
- Design and development of SaaS platforms, business tools, and custom web applications
- Frontend and backend development
- Design of robust and scalable web architectures
- Creation of REST APIs, authentication systems, and business logic
- Redesign, optimization, and evolution of existing products
- Strong product, UX, and performance sensibility
Main Stack:
- TypeScript
- React.js
- Next.js
- Node.js
- NestJS
- PostgreSQL
Types of projects I regularly manage:
- MVP
- SaaS products
- Internal tools / business tools
- Marketplaces
- Custom APIs and backends
- Web application redesigns
- Continuous evolution of products already in production
My added value:
✅ An approach that is technical, product-oriented, and pragmatic
✅ The ability to clarify complex needs and transform them into concrete solutions
✅ A very hands-on, autonomous profile, capable of moving fast without compromising quality
👉 Let's discuss your project together
French
Native or bilingual
English
Native or bilingual
German
Conversational
Spanish
Conversational
Can work on-site
Annecy (up to 20km)
Experience
- ElokenFounder & Senior Software EngineerSOFTWARE PUBLISHINGMay 2018 - Today (8 years and 1 month)Paris, FranceEnd-to-end product engineering for startups and SMEsFor over 8 years, I have been supporting startups and SMEs in the design and development of custom digital products: SaaS platforms, web applications, marketplaces, and e-commerce systems.My role involves taking a product from end-to-end, from idea validation to production launch, with a strong focus on scalability, performance, and user experience.Methodology✅ Scoping: functional specifications, business analysis, project structuring, and roadmap.✅ Architecture: sitemap, user flows, user stories, data modeling, and technical design.✅ UX/UI: wireframes, mockups, interactive prototypes, and interface validation.✅ Development: backend architecture, APIs, database, frontend integration, and DevOps.✅ Deployment & Maintenance: production launch, debugging, monitoring, and continuous evolution.Selected Projects▶️ Squarimo: complete modernization of a real estate SaaS platform with significant technical debt.▶️ Cosacq: marketplace, SaaS, back-office, and marketing site built from scratch.▶️ Doctogyneco: community platform dedicated to women's health.▶️ Bloom4Earth: headless e-commerce architecture with guided configurators.▶️ Santé-Justice: educational platform supported by public authorities.Engineering & LeadershipRecruitment and coaching of developers and designers, both in-house and freelance. Implementation of engineering standards, documentation, and coding conventions. Agile sprint management and feature prioritization. Very hands-on technical ownership of architecture, frontend, backend, and infrastructure.At Eloken, I always remained concretely involved in execution, from scoping to production. My goal: to build robust systems where technical complexity serves a clear and intuitive experience.
- CosacqChief Technology Officer (CTO)LEGALJune 2025 - January 2026 (7 months)Paris, FranceEnd-to-end product design and system architectureCosacq is a SaaS platform designed to simplify the acquisition and transfer of business assets. The project was initiated by Emmanuel Jorge, a business lawyer, with the goal of structuring a traditionally complex and fragmented legal process.Before any development, we analyzed the entire transfer cycle: key steps, regulatory constraints, friction points, stakeholders, financial implications, and responsibility allocation. This work allowed us to map the complete journey and identify the best opportunities for simplification and automation. MoSCoW prioritization then enabled us to define a solid V1 foundation.Product & Technical Execution✅ Functional Scoping: sitemap, user flows, user stories, data modeling✅ UX/UI: zoning, wireframes, high-fidelity mockups, interactive prototype✅ Architecture & Development: multi-service system, centralized authentication, monorepo, Docker environment, API-first architecture, CI/CD✅ Deployment & Maintenance: production launch, debugging, stabilization, continuous iterationKey Features Delivered▶️ Secure Authentication▶️ Dataroom with role-based access▶️ Legal document generation▶️ Administrator Dashboard▶️ Transaction Tracking▶️ Marketplace Listings▶️ Online Payments via Stripe▶️ Buyer Management CRM▶️ Blog and dynamic forms▶️ Third-party API integrationsResultsPlatform launched and in production, incubated at Université Paris-Dauphine, with a sound and scalable technical foundation.This is currently the most complete 0→1 project I have designed, combining product discovery, system architecture, and very hands-on implementation.
- SquarimoProduct OwnerREAL ESTATEFebruary 2025 - June 2025 (4 months)Paris, FranceProduct modernization and scalable frontend architectureSquarimo is a SaaS platform and real estate marketplace that modernizes property sales through a transparent, limited-time offer system, similar to an auction mechanism.ContextThe company needed to evolve an MVP into a robust, maintainable product capable of accommodating over 1,000 users, particularly in the context of a strategic partnership with Foncia. The existing codebase, which I did not develop, had significant technical debt: verbose structure, low scalability, and limited evolvability.MissionComplete redesign of the member area to ensure performance, scalability, and maintainability, while integrating new features to improve user experience.Approach✅ **Product & UX**: audit of existing journeys, identification of friction points, redesign of user journeys for sellers, buyers, and admins, UX/UI design on Figma, high-fidelity mockups, and interactive prototypes.✅ **Technical Modernization**: frontend architecture with React, Next.js, and TypeScript, integration of TailwindCSS, Shadcn, and Zod, complete frontend rebuild, implementation of authentication flows, API endpoint testing, and debugging.✅ **Delivery**: coaching of the internal apprentice developer, API validation via Postman, staging deployment, and iterative integration of new features.Results▶️ Fully modernized member area▶️ Clearer navigation and improved mobile experience▶️ More robust and scalable technical foundation▶️ Reduction of technical debt▶️ Increased autonomy for the internal team▶️ Product ready for large-scale onboardingSince this redesign, Squarimo has onboarded several thousand new users following the signing of its partnership with Foncia. The team continues to add new features on a healthier technical foundation and is preparing for expansion into Switzerland.
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Education
- Symfony 5: The Complete GuideLior Chamla2019Ce cours m'a permis de créer un e-commerce de A à Z avec le Framework Symfony et la plateforme de paiement Stripe. • Créer un système d’authentification + gestion de rôles utilisateurs • Créer une interface d'administration sur-mesure • Créer un système d'envoie d'email efficace à l'aide du composant Mailer • Créer un tunnel d'achat efficace, en plusieurs étapes avec Stripe pour le paiement (Panier, Commande, Choix du transporteur ...)
- Google CertificationGoogle2018Formation Google pour les pros - Ateliers numériques accessible en ligne Formations et Exercices. Certification obtenue