Summary: Join Yopeso as an experienced Full Stack Developer to develop and maintain a sophisticated conversational AI application, integrating multiple AI providers and offering a rich user experience. Highlights: 1. Develop and maintain frontend and backend components of an AI chat platform. 2. Collaborate on database design and optimization using MongoDB. 3. Implement and maintain real-time features using WebSocket connections. Yopeso has been developing a diverse range of software products, from large\-scale applications to smaller solutions, for 20 years. With a growing team of over 300 employees across five locations, we are dedicated to fostering a culture of growth, transparency, and professionalism. At Yopeso, we value authenticity, curiosity, and ambition. These values drive us to build strong connections within our community and with our partners, ensuring trust, integrity, and transparency in all our business practices. We strive to maintain the highest professional standards and continuously challenge ourselves to develop high\-quality, high\-performance, and secure software solutions. Our approach is rooted in efficient collaboration among passionate professionals working in agile teams. Guided by curiosity and ambition, we strive to create products that are meaningful and impactful, while remaining true to our authentic selves. We are seeking an experienced Full Stack Developer to join our team working on an open\-source AI chat platform. The successful candidate will contribute to developing and maintaining a sophisticated conversational AI application that integrates multiple AI providers and offers a rich user experience, while collaborating closely with product and design stakeholders. #### **Key Responsibilities:** * Develop and maintain both frontend and backend components of the AI chat platform * Implement new AI provider integrations and chat functionalities * Work with modern React\-based frontend and Node.js/Express backend architecture * Collaborate on database design and optimization using MongoDB * Implement and maintain real\-time features using WebSocket connections * Write comprehensive tests and ensure code quality through automated testing * Deploy and maintain containerized applications using Docker * Participate in code reviews and maintain high development standards #### **Required Technical Skills:** **Frontend Development:** * **React.js** (v18\+) with modern hooks and functional components * **TypeScript** for type\-safe development * **Vite** for build tooling and development server * **TailwindCSS** for styling and responsive design * **Radix UI** and **Headless UI** for accessible component libraries * **Tanstack Query** (React Query) for data fetching and state management * **React Router** for client\-side routing * State management with modern React patterns **Backend Development:** * **Node.js** (v18\+) with Express.js framework * **MongoDB** with **Mongoose** ODM for database operations * **PostgreSQL** structured data storage * **Redis** for caching and session management * RESTful API design and implementation * JWT and session\-based authentication **DevOps \& Infrastructure:** * **Docker** and **Docker Compose** for containerization * **MongoDB** database administration * Environment configuration and secrets management **Development Tools:** * **Git** with advanced workflows (rebasing, merging, conflict resolution) * **ESLint** and **Prettier** for code quality #### **Required Experience:** * **3\+ years** of full\-stack JavaScript/TypeScript development * **Fluent in English**, both written and verbal * Excellent communication and collaboration skills * Ability to work independently and manage complex projects #### **Nice to Have:** * Experience with **OpenAI API**, **Anthropic Claude**, or similar LLM APIs * Understanding of prompt engineering and AI model integration * **LangChain** framework for AI application development * RAG (Retrieval\-Augmented Generation) implementation experience #### **Work Arrangement:** Availability to work on\-site from our Madrid office a few days per week, with the rest of the time remote.