Senior Fullstack Developer (m/w/d) - Claude Code Expert en España

This position is listed on behalf of a partner company, who manages all applications and next steps. Our partner is looking for a Senior Fullstack Developer (m/w/d) - Claude Code Expert based in Spain. We are looking for an experienced Senior Fullstack Developer with strong expertise in AI-assisted software development, particularly Claude Code, to support the launch and continued evolution of an innovative online marketplace for life coaching and counseling. You will help finalize essential product features, strengthen development practices, and transition the platform from active development into stable operations. With a strong focus on backend engineering, you will build reliable APIs, secure authentication systems, and scalable cloud-based integrations. You will also contribute to frontend development, infrastructure evaluation, and long-term technical planning. Working alongside an experienced team, you will have the autonomy to introduce best practices, solve complex engineering challenges, and influence important technical decisions. This opportunity is ideal for a proactive developer who values clean code, creative problem-solving, and building technology with a meaningful real-world impact. Accountabilities: You will take a leading technical role in preparing the platform for launch and ensuring its continued stability, performance, and scalability throughout the post-launch phase. - Finalize the development and implementation of key product features required for the initial marketplace launch. - Support the transition from active development to operational delivery, establishing reliable processes for deployment, maintenance, and ongoing improvements. - Establish and promote engineering best practices, including clean code standards, maintainable architecture, testing, and efficient development workflows. - Leverage AI-powered development tools, particularly Claude Code, to accelerate implementation, improve productivity, and maintain high-quality software. - Design, develop, and maintain backend services and REST APIs using TypeScript, Node. js, and Express. - Build and manage cloud-based solutions within the Firebase and Google Cloud Platform (GCP) ecosystem.

- Implement secure authentication and authorization mechanisms using Firebase, OAuth 2. 0, and JSON Web Tokens (JWT). - Develop and maintain GitHub-based CI/CD pipelines for Firebase Functions across development, staging, and production environments. - Integrate and maintain third-party services, including Twilio for communications and Stripe for payment processing. - Support frontend development and improvements using SvelteKit, Svelte, TypeScript, and Tailwind CSS, ensuring responsive and accessible user experiences. - Evaluate and benchmark the existing IT infrastructure, identify areas for improvement, and contribute to the technical roadmap. - Troubleshoot technical issues, improve system reliability, and support ongoing platform optimization after launch. - Collaborate with team members across product and technical functions, taking ownership of key deliverables and contributing to broader company development initiatives. Requirements: The ideal candidate is a technically strong fullstack developer with advanced TypeScript and backend engineering skills, practical experience with cloud-based applications, and a proven ability to use AI coding tools effectively. - Extensive experience in AI-assisted software development, preferably using Claude Code in real-world development workflows. - Advanced proficiency in TypeScript, particularly for backend application development. - Strong experience with Node. js and Express for building and maintaining server-side applications. - Hands-on experience with Firebase and the Google Cloud Platform ecosystem. - Deep understanding of REST API design, including methods, status codes, error handling, and API reliability. - Experience implementing OAuth 2.