AI Full Stack Developer

This is a fully remote position, open to applicants in Spain.

📋 Description

• As a Full-Stack Developer within the AI-LAB, you will play a crucial role in developing and scaling our AI products.

• You will manage features from inception to completion across a modern Next.js frontend and our NestJS backend services, ensuring a seamless and powerful user experience.

• Develop and maintain features on our Next.js (App Router) frontend utilizing TypeScript, SWR, Tailwind, and a component-driven design system, with full internationalization (i18n) support.

• Design, implement, and uphold RESTful APIs using NestJS (TypeScript) to manage authentication, data processing, billing, usage tracking, and the orchestration of AI workflows.

• Take ownership of backend services end-to-end: from schema design and migrations to deployment and observability, while also contributing to the development of new services as the product surface expands.

• Integrate and manage third-party SDKs and APIs that enhance critical product flows, including payment processing, authentication, analytics, and messaging.

• Build AI agents and tools utilizing the Claude SDK and Model Context Protocol (MCP): providing LLMs with real-time access to data, APIs, and tools to enable them to take meaningful actions on behalf of users.

• Contribute to schema design with Prisma and PostgreSQL, writing and reviewing migrations, and thoughtfully considering data models that evolve safely over time.

• Implement and uphold feature flags, A/B experiments, and analytics events to ensure product decisions are data-driven.

• Manage incoming webhooks and asynchronous task processing with the precision necessary for payment-critical and PII-handling code paths (idempotency, retries, fault tolerance).

• Collaborate with AI product managers and AI specialists to translate complex requirements into robust, scalable features—and advocate for simpler solutions when applicable.

• Work together on application deployment and assist in maintaining our cloud infrastructure.

⛳️ Requirements

• TypeScript Proficiency: Highly skilled in TypeScript across both frontend (React/Next.js) and backend (Node.js/NestJS) environments.

• Frontend Expertise: Extensive experience with React and Next.js (App Router): Server Components, route handlers, streaming, metadata, i18n, and modern data-fetching patterns (SWR or equivalent).

• Backend Expertise: Strong experience in building production REST APIs with NestJS (or similar Node frameworks like Express/Fastify): modules, DI, guards, interceptors, DTO validation.

• Database Skills: Proficient with PostgreSQL and an ORM such as Prisma. Comfortable writing and reviewing migrations, reasoning about transactions, and designing schemas that safely evolve.

• API Integration Depth: Proven experience in integrating third-party SDKs: managing webhooks, idempotency, retries, and asynchronous fulfillment.

• Problem-Solving Mindset: Collaborative and pragmatic, willing to question assumptions and highlight tradeoffs before coding.

• Passion for AI and High Agency: Genuine enthusiasm for AI products, coupled with a desire to introduce new techniques and tools proactively within the team.

• Creativity and Proactivity: Enjoy proposing features, discovering creative solutions, and enhancing the user experience without needing direction. A dedicated self-learner who adapts to new tools and platforms rapidly.

• Nice to Have: Previous experience with payment/subscription systems. Familiarity with monorepo tooling (pnpm workspaces, Turborepo, Nx). Experience with BigQuery and event-pipeline analytics. Knowledge of Tailwind and component-driven design systems. Understanding of cloud platforms such as Google Cloud Platform (GCP). Experience with feature-flag systems. Prior work on AI products or LLM-powered applications.

🏝️ Benefits

• Competitive salary, full-time permanent contract, and premium private health insurance (including dental and psychological services).

• 25 days of vacation plus your birthday off, with flexible vacation options—no blackout days!

• Work-life balance: Enjoy a flexible schedule with flextime and the option of working fully remote or from our Barcelona office.

• Benefit from free Friday afternoons with a 7-hour workday, in addition to a 35-hour workweek during July and August so you can enjoy the summer!

• Growth and career development: At Leadtech, we prioritize your growth. Enjoy a flexible career path with personalized internal training and an annual budget for external learning opportunities.

• Unique Perks: Office in Barcelona equipped with complimentary coffee, fresh fruit, snacks, a game room, and a rooftop terrace offering breathtaking Mediterranean views.