Lead Backend AI Engineer - Developer Platform

Healf is Europe's fastest-growing company. Number one on the FT1000, number one on the Sifted 100. From £1m to over £100m in under three years, with a small, talent-dense team and an electric culture with day one founder intensity. Now we're aiming for £1bn in the next three. We curate the world's best wellbeing brands across The Four Pillars™: EAT, MOVE, MIND, SLEEP. That's the first chapter. The next chapter is harder and more interesting. We are moving from one market to many, from e-commerce to a technology platform, and from curating wellbeing to defining it. We are a health company, so we think we should act like one. At its fullest expression, Healf redefines what wellbeing means for tens of millions of people. About the Role Healf is Europe's fastest-growing health and wellness company — number one on the FT1000 and Sifted 100. We have gone from £1m to over £100m in under three years, and we are building the technology platform that takes us to £1bn. That means every engineering decision made now shapes what is possible for tens of millions of people. As our Founding AI Engineer on the Developer Platform team, you will build the foundational platform systems that drive engineering quality, reliability, and velocity across the organization. You will own the development of core platform capabilities, including identity, authentication, authorization, and other critical infrastructure services. In addition, you will design and build AI-powered agents and developer tooling to accelerate software development and improve quality—ranging from AI-assisted coding and automated QA to incident detection, monitoring, and operational workflows. Your work will enable engineers to move faster while maintaining high standards of reliability and performance. You will define the technical architecture, make key infrastructure and platform decisions, and play a central role in shaping our engineering foundations. Over time, you will have the opportunity to build and lead a small team around this function. This is a true 0-to-1 role with significant ownership, direct partnership with the CTO, and meaningful equity participation. What You Will Do Architect and Build: Core platform services including Identity, Authentication, Authorization, and other foundational backend systems used across engineering teams. AI Agents / Harnesses: Build AI agents and developer productivity tooling to accelerate coding, automate bug fixing through Slack and Linear, enable AI-powered QA testing, and drive intelligent incident monitoring and resolution. Own: The core engineering infrastructure, ensuring scalability, reliability, security, and ongoing cost optimization. Set the Technical Foundation: Define key architectural decisions across the technology stack, deployment model, platform architecture, and data systems. Lead / Mentor: Mentor junior engineers and help establish engineering best practices, technical excellence, and a high-performance culture. What We Are Looking For Hands-on experience building and operating core platform systems such as Identity, Authentication, Authorization, and shared backend infrastructure. Hands-on experience developing AI agents and automation systems for engineering workflows including coding, debugging, testing, incident management, and developer productivity. Strong architecture instincts; able to quickly reason through complex system design problems and make sound technical trade-offs. Strong backend engineering experience with AWS and excellent proficiency in Python. Experience with AI orchestration frameworks and tooling such as LangGraph, LangChain, or similar agent-based development frameworks. Experience building and maintaining CI/CD pipelines, automated testing infrastructure, and modern software delivery systems at scale. Comfortable balancing deep individual contributor work with mentoring and supporting other engineers. Nice to Have Experience at a developer tooling, infrastructure, platform, or AI-first company. Experience building internal developer platforms or engineering productivity systems. The Deal Competitive and meaningful compensation package for the right person. We ask a great deal of the people who work here. We expect full ownership and a genuine commitment to give this chapter everything you have. In return, we will give you the same: everything we have, invested in your growth, your wellbeing, and the defining skills of the next decade. We have built the fastest-growing company in Europe with a team small enough that every person in it shapes the outcome. That is still true today. The next person we hire will change the trajectory of the company. If the most important work of your career is ahead of you, this is the place to do it.