337 Best train engineer Jobs in United Kingdom (April 2026)

Founding Engineer

5 days ago

City of London

Founding Engineer Wellbeing Intelligence · Healf The builder. The one who is genuinely obsessed with what comes next. Not the technology stack. Not the architecture pattern. The thing underneath: the systems instinct, the zero-to-one appetite, the compulsion to build things that actually scale. You might be a staff engineer at a growth-stage company. You might be a principal at a larger tech firm who’s been quietly architecting the product others will inherit. There are engineers who built the first versions of Spotify’s recommendation engine, Monzo’s core banking layer, and Deliveroo’s dispatch system, products that now feel inevitable, who started exactly where you are now: staring at a blank canvas with a hard problem and no playbook. We don’t care about the title. We care about whether you have the technical depth to design a system from first principles, the product intuition to build for real users, and the conviction to make decisions with long-term consequences when no one is looking over your shoulder. Healf is Europe's fastest-growing health platform. £100M+ revenue run-rate. 700k+ customers. A high-retention, high-margin marketplace. Strong brand and distribution. We curate the world's best wellbeing products across EAT, MOVE, MIND, and SLEEP. That's the first chapter. The next chapter is harder and more interesting. Today, wellbeing decisions are primitive. Customers guess. They follow influencers. They try products and hope. We are building the system that changes that. A personalised wellbeing intelligence engine that understands behavioural patterns, captures longitudinal health data, and builds smart AI agents that help customers solve their wellbeing needs. A closed feedback loop. A decision engine, not just a marketplace. If we get this right, we don't just sell products. We become the operating system for how the world lives well. This is a 0→1 opportunity to build a net-new business line that could drive up to £250M in annual revenue in the next three years. You will build it from scratch. Why this role is Healf At Healf, we think engineering judgment is one of the most important forms of capital allocation in the company. Every architectural decision made in the next twelve months determines what is possible in the next five years. Every hire you make changes what the platform can become. That is why we do not see this as a conventional engineering leadership role. Engineering leadership is the functional label. Defining what a next-generation wellbeing intelligence platform looks like is the real job. We are not laying down tracks. We are deciding where the train goes. Somewhere right now there is a principal engineer at a Series B health-tech company who has spent three years making the right calls quietly. Who designed the system that works. Who has said no to things that looked fast but would have cost the company two years of rework. That person probably has never heard of Healf. They wouldn't click on a LinkedIn InMail. But if someone who understood what they actually cared about reached them with the right story at the right moment, they would listen. There is also a founding engineer at a well-known consumer tech company who is twelve months past the point where the work became maintenance. Who built the thing, watched it scale, and is now ready to build the next thing. They are not looking. But they are ready. These are the people we want. And this is the role those people will take. What you’ll own → The architecture. You will design the full wellbeing intelligence stack from first principles. Backend, data, ML systems. Infrastructure capable of learning from live user interaction. The choices you make in the next six months will define what's possible in year three. You will own those choices. → The build vs buy decisions. Every platform team reaches these inflection points. You will own them with authority and with the context to make them well. → The engineering principles. Not a style guide. The actual principles that govern how your team thinks about quality, velocity, and long-term consequences. You will define what good looks like here. → The technical strategy. You will partner directly with the CTO. This is not advisory. You will have real authority over the direction of the intelligence layer and the product platform it powers. → The team. You will grow and mentor the engineers who build alongside you. Every person you bring in raises the floor. You will build the nucleus that scales wellbeing intelligence. → The product feedback loop. You will work cross-functionally with Product and Design to ship. You will build via continuous experimentation. You will be close to real users and real outcomes. What you'll deliver in the first 12 months → A production-grade intelligence layer powering personalised decisioning for hundreds of thousands of customers → A scalable data architecture designed for international growth from the start → A high-talent engineering nucleus built around your judgment → Clear product differentiation driven by intelligence, not curation alone → A platform that others in health tech study and try to replicate Why you’re Healf You have built something from zero. Not joined after product-market fit. Not inherited a working system. You architected something from the beginning and watched it scale to meaningful usage. You know what that feels like in both directions — the early ambiguity and the later scale. You have made platform-level decisions with long-term consequences. And you have lived with them long enough to know which ones you got right. You have built or integrated ML and data-driven systems in production. Not in notebooks. Not as experiments. Shipped, live, used. You have influenced technical direction beyond your immediate team. Not through authority. Through judgment that others trusted. You have operated in a high engineering bar environment where architectural thinking was respected and expected. You are not looking for the next job. You are looking for the thing worth building next. The reality This is hard. It requires speed and precision. It requires building for scale without overbuilding. It requires making good decisions in conditions of genuine ambiguity, with real consequences, and without the luxury of consensus. You will sometimes be wrong. What matters is that your judgment compounds over time and your errors get smaller as the system gets bigger. If you want to spend the next two years building something foundational that others will be building on for a decade, this is that opportunity. Show us → A system you architected from zero. What were the first principles you started from? What did you get right early that saved you later? What did you get wrong, and how did it shape the next decision? → A build vs buy decision with real stakes. What did you choose, why, and what happened? → A moment where you saw how something would break six months before it did. What did you do with that knowledge? → An engineer you hired or developed who became better than you expected. What did you see in them that the CV didn't show? → Evidence that you can work at the intersection of engineering and product. Not just clean systems. Systems that serve real users. The deal Competitive base. Meaningful equity. Direct access to leadership from day one. We ask a great deal of the people who work here. Full ownership. Genuine commitment. Everything you have, for this chapter. In return, we will give you the same: the resources to build properly, a team worth leading, and the creative authority to do work that defines your career. We have built the fastest-growing health 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 platform. If the most important work of your career is ahead of you, this is the place to do it.

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