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 ..... full job details .....