Senior AI Software / Product Engineer

Senior AI Software Engineer London (Hybrid, 3 days per week) Up to £140,000 + Equity We're partnered with a fast-growing AI start-up building cutting-edge behavioural intelligence technology for the financial services sector. Backed by an exceptional leadership team and industry experts, they're developing a platform that helps organisations better understand client behaviour through advanced AI and large language models. As their first senior individual contributor engineering hire, you'll play a critical role in shaping both the product and engineering culture from the ground up. The Opportunity This is a true 0-to-1 product engineering role. You'll work closely with senior leadership to build and scale a greenfield product, taking ownership across the full stack while driving the architecture and evolution of production-grade AI systems. You'll have significant influence over technical direction, engineering standards, product decisions and future hiring as the team grows. What You'll Be Doing * Building and shipping customer-facing product features end-to-end * Developing and scaling production LLM applications * Owning RAG pipelines and AI application architecture * Implementing guardrails, evaluations, caching and model routing strategies * Working across TypeScript, React, Node.js, PostgreSQL and AWS (Open to different technology backgrounds!) * Building API-first services for enterprise customers * Establishing engineering best practices around testing, deployment and code quality * Collaborating directly with product and leadership stakeholders to influence roadmap and delivery priorities What We're Looking For * Experience building and scaling production LLM-powered applications * Strong full-stack engineering background * Experience delivering secure, reliable and scalable systems * Comfortable working across multiple technologies and learning new stacks quickly * Experience with React and modern web applications * Product-minded approach with the ability to operate autonomously * Passion for building in an early-stage, high-growth environment * Experience within regulated industries or financial services is beneficial but not essential Why Join? * Up to £140,000 base salary * Meaningful equity package * Opportunity to become the first senior engineering hire * Direct impact on architecture, product and company direction * Work alongside talent from leading technology and AI organisations * Greenfield product with genuine product ownership * Hybrid working in Central London * 25 days holiday plus additional benefit