Senior Full Stack AI Native Developer

Senior Full Stack AI Native Developer

Leadtech is seeking a talented and proactive Senior Full Stack AI Native Developer to join our Development team. In this role, you will be instrumental in building and scaling our platforms and products, working across our entire AI technology stack to deliver a seamless and powerful user experience. You will be joining projects with a fast-paced approach and a modern tech stack.

About the Role

As a Senior Full Stack Developer, you will:

• Design, implement, and maintain RESTful APIs using NextJS/Express for user authentication, data processing, and analysis workflows.
• Build AI agents using the Claude SDK to access real-time data, APIs, and tools, enabling them to take actions and integrate LLM reasoning with real-world applications.
• Develop AI agents with LangGraph + LangFuse to handle multi-step reasoning, collaborative workflows, and task handoffs between agents, while maintaining conversation state and context.
• Develop and maintain features for both our React frontend and Node.js (NextJS) backend.
• Build intuitive user interfaces using TypeScript, Vite, React, and our UI component library, allowing users to manage media, analyses, and interact with our web product.
• Integrate our platform with various external services, such as Payment Service Providers, and handle incoming webhooks for asynchronous task processing.
• Collaborate closely with AI product managers and AI specialists to translate complex requirements into robust, scalable features.
• Contribute to database schema design and write migrations for PostgreSQL & BigQuery databases.
• Collaborate with the team on application deployment and help maintain our cloud infrastructure on Google Cloud Platform (GCP).

Requirements

We are looking for a skilled developer passionate about building modern, data-driven applications.

• Extensive experience with TypeScript, particularly in both frontend (React) and backend (Node.js) environments.
• Strong frontend expertise with React, including modern state management, Hooks, and the Context API.
• Solid backend expertise in building and consuming REST APIs with Node.js and NextJS or Express.
• Experience with databases like PostgreSQL and working with an ORM or query builder.
• Knowledge of LangGraph, LangChain, and LangFuse.
• Deep API integration experience with third-party vendors, including working with various SDKs.
• A proactive, self-learning mindset, with the ability to quickly adapt to new tools and platforms.
• A problem-solving mindset and a collaborative approach.
• A genuine passion for and awareness of artificial intelligence and a strong desire to build products leveraging its capabilities.
• High agency and the ability to work autonomously with a large degree of freedom.
• Creativity and proactivity in proposing new features and finding solutions to improve user experience.
• Experience with the Python framework is also required.

Nice to Have:

• Previous experience working on AI, machine learning, or large language model (LLM) projects.
• Familiarity with UI component libraries.
• Knowledge of cloud platforms like Google Cloud Platform (GCP).

What We Offer

• High-Impact Role: Be a key player in a small, agile team building a greenfield project with the potential to transform an industry.
• Modern Technology: Work with a cutting-edge, carefully selected tech stack focused on best practices.
• Growth & Learning: Gain deep experience in AI-driven applications, cloud-native architecture, and real-time systems. Enjoy a flexible career path with personalized internal training and an annual budget for external learning opportunities.
• Stability & Vision: Experience the energy of a startup environment backed by the resources and stability of a large, successful company.
• Collaborative Culture: We value open communication, teamwork, and a shared passion for building exceptional products.
• Work-Life Balance: Benefit from a flexible schedule with flextime and the option of working full remote or from our Barcelona office. Enjoy free Friday afternoons with a 7-hour workday, plus a 35-hour workweek in July and August.
• Comprehensive Benefits: Competitive salary, full-time permanent contract, and top-tier private health insurance (including dental and psychological services). 25 days of vacation plus your birthday off, with flexible vacation options.
• Unique Perks: If you choose to work from our Barcelona office, you'll find free coffee, fresh fruit, snacks, a game room, and a rooftop terrace with stunning Mediterranean views. Additional benefits include ticket restaurant and nursery vouchers.

Leadtech is an Equal Employment Opportunity Employer. We encourage applications from people with diverse backgrounds, interests, and personal circumstances.

Join us in an environment where you’re free to innovate, learn, and grow alongside passionate professionals. We’re looking forward to getting to know you!