Nicolas Guenin Senior frontend engineer

Hi! With 10+ years of experience, I build scalable and high-performance web applications.

Helping product teams ship faster by designing robust architectures, improving performance, and raising code quality standards is my focus.

Focused on long-term maintainability, pragmatism, and delivering impact over complexity, I strive for solutions that last.

Skills

Expertise Areas

  • Frontend architecture: Building scalable frontend architectures for large apps with micro-frontends, monorepos, FSD/modular structures, and web-components, enabling teams to ship faster and maintain scalability.
  • Performance & Optimization: Web-vitals, lazy loading, code-splitting, runtime performance tuning
  • Code Quality & Best Practices: SOLID, DRY, TDD; mentoring teams on maintainable code and improving CI/CD pipelines.
  • Security & Accessibility: OWASP compliance, WCAG standards, secure data handling.
  • API Integration: Designing frontend applications tailored to REST, OpenAPI, BFFs, API gateways, and realtime databases, accustomed to distributed backends leveraging SAGA and event-driven patterns.
  • Design Systems & UX tooling: Experienced in building and maintaining design systems, collaborating with Figma and Storybook to ensure consistent, reusable frontend components.

Technical stack

  • Languages: JavaScript, TypeScript, Node.js
  • Frameworks/Libraries: React, Vue, Next, Nuxt
  • Styling & UX: HTML, CSS, SASS, LESS, PostCSS, CSS-in-JS
  • Build & DevOps: Webpack, Vite, Rspack, Docker, GitLab CI, Module federation

Testing & CI/CD

  • Unit & integration tests (Jest, Vitest, Testing Library, Mocha)
  • Optimizing CI/CD pipelines for reliable and fast delivery

Some talks

Experiences

Senior Frontend Engineer — Believe (Current) | Accounts & Contracts Team

  • Contributed to a large-scale application using module federation and NX, collaborating closely with backend, product, and design teams to drive features forward.
  • Introduced FSD architecture on the frontend, adopted by multiple teams after demonstrating its effectiveness in scaling and maintainability.
  • Contributing to the design system: restructured foundations, developed major components, improved Storybook organization, and enhanced stories with MDX format.
  • Produced documentation and best practices to help developers create and maintain reusable components efficiently.
  • Optimized the monorepo CI pipeline, splitting it into sub-pipelines to improve build speed and developer workflow.
  • Acted as a cross-team technical resource, ensuring consistency, scalability, and maintainability across the frontend ecosystem.

Lead frontend Engineer - Yogosha 2022- 2024

  • Supervised and guided the frontend team, establishing best practices, optimizing CI/CD pipelines, and ensuring maintainable and scalable code.
  • Led a major frontend stack migration, modernizing the architecture and improving performance, scalability, and developer experience.
  • Designed and implemented the design system from scratch, with documentation and tooling to support scalable component development.
  • Re-structured the monorepo and introduced FSD architecture, standardizing frontend patterns across projects.
  • Developed core features: task manager (internal Jira-like tool), Appliance application (handling secrets/configmaps for Helm/Kubernetes), PKCE authentication module with Keycloak, and data visualization components.
  • Implemented asymmetric encryption (EC25519, RSA) in Node.js
  • Delivered both SaaS and self-hosted versions, including customizable theming (grey-label) and Keycloak themes.
  • Ensured OWASP compliance and security best practices, critical for a cybersecurity-focused product.
  • Contributed to the overall frontend architecture, enabling scalable, maintainable, and secure solutions across the platform.

Senior frontend engineer - LoisirsEnchères 2019 - 2022

  • Led the complete rewrite of the e-commerce and admin applications, modernizing the frontend architecture and technical stack.
  • Developed key business features including real-time bidding, chat system, and price negotiation module.
  • Built Node.js microservices and an API gateway to support scalable backend architecture.
  • Worked with a Firebase realtime database, handling UI/UX challenges related to live updates and asynchronous data flows.
  • Improved frontend performance from 40 to 94 on Lighthouse, significantly enhancing user experience and loading times.
  • Established frontend best practices and maintainable architecture standards.

Frontend developer - SEPPA 2017 - 2019

  • Developed a SaaS CMS platform enabling clients to generate responsive, production-ready commercial landing pages deployable to their own servers.
  • Built a modular system to integrate user experience tracking and marketing analytics, empowering marketing teams with actionable insights.
  • Contributed to the development of the platform’s Node.js API, supporting scalable content management workflows.
  • Delivered multiple websites and e-commerce platforms, ensuring performance, responsiveness, and maintainable frontend architecture.

Freelance

  • Delivered custom websites and e-commerce platforms for local businesses, managing projects from requirements to production.
  • Collaborated directly with clients to define technical solutions aligned with business needs.
  • Ensured responsive design, performance optimization, and maintainable frontend architecture.

Frontend developer - Buzz Agency 2015 - 2017

  • Developed custom websites for companies across various industries, delivering responsive and production-ready solutions.
  • Contributed to the development of an event registration platform for medical conferences, enabling secure attendee management and streamlined registration workflows.
  • Ensured performance, cross-browser compatibility, and maintainable frontend code.

Volunteer developer - Connect Lab 2015 - 2016

Volunteer developer

  • Maintained and evolved the association’s website, ensuring stability, performance, and content updates.
  • Contributed to the organization of the annual startup event, supporting project founders in pitching their solutions to investors and partners.