Senior Fullstack Developer - AI Applications
23 hours ago
Santander
About the Opportunity We're partnering with a stealth AI company building infrastructure that powers reinforcement learning (RL) environments for some of the world's leading AI labs. Their systems operate directly within the AI training loop, helping evaluate, improve, and deploy next-generation AI models. This is highly applied, production-focused engineering work with real-world impact. We're looking for exceptional Full-Stack Software Engineers who thrive in fast-paced environments, take ownership, and can independently ship complete applications from idea to deployment. What You'll Do • Build full-stack applications end-to-end (frontend, backend, and infrastructure), • Transform loosely defined concepts into production-ready products, • Design and implement systems supporting AI agents and RL workflows, • Deliver high-quality software rapidly without sacrificing maintainability, • Collaborate directly with founders, researchers, and engineering leadership, • Own projects from specification to deployment with minimal oversight How You'll Work • Operate with a high degree of autonomy and ownership, • Use modern AI coding tools (Cursor, Claude Code, Codex, etc.) to accelerate development, • Review and validate all AI-generated code, • Make architectural decisions independently, • Work primarily through asynchronous communication (Slack), • Move quickly while maintaining engineering excellence RequirementsCore Technical Skills • Strong experience building and shipping complete software products, • Frontend development with:, • React, • TypeScript, • Modern UI frameworks, • Backend development with:, • Python, • FastAPI, • REST APIs & integrations, • Database design and implementation, • System design, debugging, and performance optimization, • Writing clean, scalable, production-quality code Nice to Have • Experience with LLMs, AI agents, or AI-powered applications, • Experience building data pipelines or web scraping systems, • Startup, freelance, or rapid-delivery environment experience, • Familiarity with modern AI-assisted development workflows Ideal Candidate You are someone who: ✅ Has built and deployed multiple real-world applications ✅ Can own systems end-to-end without constant guidance ✅ Thinks in systems, not just tasks ✅ Uses AI as a productivity multiplier, not a replacement for engineering judgment ✅ Enjoys solving ambiguous problems and creating structure where none exists Contract Type We welcome both freelance contractors and candidates interested in a long-term/full-time opportunity. The engagement starts with a paid project, allowing both sides to evaluate fit, delivery quality, and collaboration. High-performing engineers may continue on future projects or transition into a longer-term role.
Benjamín G.Active 2 hours ago
