frontend js/react/typescript for AI products

Leadtech's AI-LAB researches, prototypes, develops, launches, and scales challenging AI products across the Leadtech portfolio. The team operates within a diversified app portfolio with millions of active users and mature data infrastructure.

• Take new products from ideation and research through prototyping, build, release, and scaling, owning features end-to-end;
• Prototype concepts rapidly, test them with users, and decide whether to iterate or discard them based on findings;
• Scale successful products by hardening the codebase, maintaining performance and quality, and evolving features based on user behavior;
• Own frontend architecture, the component library, the design system, and product UX;
• Design and build high-converting landing pages, checkout flows, and paywalls;
• Design and integrate LLM-powered features into products;
• Create skills, automations, and internal tooling that improve team efficiency;
• Instrument features, run experiments, analyze funnel data, and iterate based on results.

• 5+ Years of frontend engineering experience;
• Deep proficiency in TypeScript and React, including Hooks, Context API, state management, Vite, Tailwind, and Shadcn UI;
• Experience owning significant product surface area;
• Ability to distinguish and articulate good and bad UX, with examples from personal work;
• Comfortable working in Figma, with knowledge of typography, spacing, and motion;
• Experience building durable design systems and component APIs;
• Experience with responsive, mobile-first layouts, accessibility, and frontend performance, including bundle size optimization;
• Ability to distinguish prototypes from production code designed for a growing user base;
• Regular practical use of AI throughout the development process, including building personal skills, agents, or automations;
• Experience with marketing sites, landing pages, or checkout flows and understanding of conversion drivers;
• Experience running or interpreting A/B tests and distinguishing meaningful results from noise;
• Backend foundations in Node.js, Express, REST APIs, and PostgreSQL;
• Ability to work autonomously on ambiguous problems, make decisions, surface questions early, and collaborate clearly across functions;
• Self-driven and business-aware approach focused on real problems and measurable impact;
• Nice to have: Previous experience launching and scaling products in a startup, venture studio, or internal product team; hands-on SEO experience including technical audits, SSR/SSG rendering strategy with Next.js, structured data, and international or multi-market pages; familiarity with Amplitude and GA4; LLM engineering experience with prompt tuning, RAG pipelines, vector databases, or agentic frameworks; passion for AI and staying current with new models, protocols, and developer tooling.

• Competitive compensation package and benefits;
• Flexible hours and flextime;
• Health insurance, including dental and psychological services;
• Training, personalized internal training, and an annual budget for external learning opportunities;
• Competitive salary;
• 25 Days of vacation plus a birthday day off, with flexible vacation options and no blackout days;
• Free Friday afternoons with a 7-hour workday;
• 35-Hour workweek in July and August;
• Free coffee, fresh fruit, snacks, game room, and rooftop terrace at the Barcelona office;
• Ticket restaurant and nursery vouchers paid directly from gross salary.