Senior Backend Engineer

Do Health; Greater London; On-site; GBP 90,000 - 130,000; Full time

Job summary

Do Health is hiring a Founding Backend Engineer to own major backend features end-to-end, shape architecture with the lead engineer, and scale our blood-testing infrastructure across the UK and beyond. You will build production AI systems that personalize health data at scale and improve reliability and observability as the product grows.

You will work closely with product, design, and clinical teams in a fast-paced startup environment, with strong ownership and minimal layers between you and

Qualifications

• 5-8 years of backend experience with strong fundamentals.
• Experience at a startup or scale-up where you owned things; architectural thinking.

Responsibilities

• Own major backend features end-to-end - design, build, ship, monitor, iterate.
• Shape architecture with the lead; make real technical decisions.
• Scale blood testing infrastructure across the UK and internationally.
• Build production AI systems - personalization engines that use longitudinal data at scale.
• Improve reliability, observability, and foundational systems as the product grows.
• Collaborate directly with product, design, and clinical teams.

Skills

Backend development

Architectural thinking

End-to-end systems design

Reliability engineering

AI tool usage

Decision making in ambiguity

Tools

TypeScript/Node.js

Go

Python

Job description

Do Health is a mobile-first preventative health product, co-founded by Dr Rangan Chatterjee and built as an independent startup inside Voy - one of the UK's fastest-growing digital health companies (more than 100% YoY growth every year since inception, ~750k active customers across the UK, Germany, Brazil and India), already working across metabolic health, menopause, hormonal health, TRT and dermatology. Do Health is Voy's next chapter: the first product built not to treat illness, but to prevent it. We test people's blood regularly, track how it changes over time, and turn results into a personalised programme across four pillars - Eat, Move, Sleep, Relax - that helps someone make small changes they can actually keep.

The Opportunity

We're hiring a Founding Backend Engineer at Do Health - a mobile-first preventative health product co-founded by Dr Rangan Chatterjee, built as an independent startup inside Voy.

Voy is one of the UK's fastest-growing digital health companies (£300M+ revenue, doubling next year, ~2x YoY growth across men's health, metabolic health, menopause, hormonal health, TRT, dermatology and more). Do Health is its next chapter: the first product designed not to treat illness, but to prevent it.

The product combines regular blood tests, longitudinal health data, behaviour-change science and AI personalisation to help people make better lifestyle decisions over time. We already run AI systems in production at a scale very few UK companies match.

You'd join a 10-person team, partnering directly with our lead engineer on the backend. There's no layer of management between you and the work. What you ship in month one is what users get.

What You’ll Do

• Own major backend features end-to-end - design, build, ship, monitor, iterate. Not "contribute to" - own.
• Shape architecture alongside the lead. Real technical decisions, made by you, kept or changed based on what works.
• Scale our blood testing infrastructure across the UK and internationally as we expand.
• Build production AI systems - personalisation engines that act on longitudinal health data at scale.
• Improve reliability, observability, and the foundations that everything else depends on as the product grows.
• Work directly with product, design, and clinical teams. No tickets thrown over walls.

Who You Are

• 5-8 years of backend experience with strong fundamentals. We care more about depth than years.
• Experience at a startup or scale-up where you genuinely owned things.Architectural thinking.
• You can hold an end-to-end technical conversation about systems you've built - what trade-offs you made, what broke, what you'd do differently.
• A track record of shipping reliable systems. Not just features - the boring infrastructure that keeps them up.
• Comfort with judgement calls in ambiguous situations. Most decisions here don't have a clear right answer.
• Confident, responsible use of AI tools in your workflow. Not "vibe coding" - using them as a force multiplier where they help, ignoring them where they don't.

Nice-to-have, Not Required

• Strong TypeScript / Node.js experience (it's our primary stack, but we'll happily hire someone excellent in Go, Kotlin, Python or similar)
• Experience scaling systems to high user volumes
• Exposure to ML/AI systems in production
• Healthcare or regulated-industry experience