Full job descriptionSenior 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