Développeur(se) Fullstack Next.js

This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Développeur(se) Fullstack Next.js based in France. As a Fullstack Next.js Developer, you’ll join a lean, high-performing technology team building and scaling an AI-powered SaaS product with strong market traction. You’ll take ownership of the application’s server-side layer while also collaborating closely with front-end developers on product delivery. The role offers substantial technical responsibility, from data access and authentication to complex business logic and third-party integrations. You’ll work with a modern stack including Next.js, TypeScript, Tailwind, and shadcn, with AI tools integrated into the development workflow. The environment is fast-paced, autonomous, and focused on shipping high-quality software rather than basic CRUD development. This is an opportunity to become a key technical contributor to a growing product while helping shape its continued evolution. Own the application back end integrated directly into the Next.js application, including Server Actions and API Routes. Design and manage efficient data access and the underlying application data layer. Develop and maintain third-party integrations and authentication mechanisms. Implement and optimise complex business logic, including credit management, job pooling, and API timing or delay management. Collaborate closely with front-end developers to support seamless integration and ensure consistent product experiences. Contribute directly to the product roadmap and deliver features aligned with business and user needs. Act as a technical contributor who proactively proposes improvements and solutions rather than simply executing predefined specifications. Write clean, maintainable, robust, and sustainable code that can evolve with the product. Investigate and address performance challenges to ensure a reliable and responsive application. Integrate AI-powered development tools into the engineering workflow while applying appropriate technical judgement to their output. Communicate effectively within a fully remote team and maintain strong alignment across development activities. Remain adaptable and, when required, contribute to other products within the wider SaaS portfolio. Requirements: 5–10 years of professional fullstack development experience, with a level of seniority allowing you to take ownership of the application back end. Proven experience working in SaaS environments and delivering production-grade web applications. Strong hands-on expertise with Next.js, particularly its integrated server-side capabilities such as Server Actions and API Routes. Solid experience with data access, third-party integrations, authentication, and complex application business logic. Strong TypeScript skills and practical experience with Tailwind CSS and shadcn. Good understanding of modern meta-frameworks, with Next.js experience preferred; familiarity with alternatives such as TanStack Start or Nuxt is a plus. Ability to design and implement clean, maintainable, modular, and scalable code. Comfortable using AI-assisted development tools as an integral part of the engineering workflow. Strong autonomy and ownership, with the ability to take responsibility for a significant technical area of a product. Collaborative mindset and ability to work closely with front-end developers and other technical stakeholders. Strong remote communication skills and ability to work effectively within a distributed team. Proactive approach, with a willingness to challenge assumptions and suggest technical or product improvements. Fluent French is essential, as it is the team's primary working language. Sufficient English proficiency to communicate effectively in a professional environment. Benefits: 100% remote working opportunity from anywhere in Europe. Choice of a permanent employment contract or long-term freelance engagement, depending on circumst