Senior Backend Engineer - Do Health

Worky; Greater London; On-site; GBP 90,000 - 150,000; Full time

Job summary

Do Health seeks a Founding Backend Engineer to join its fast-growing team inside Voy. You’ll own core backend systems, design scalable architectures, and ship features end-to-end in a tightly coupled, product-focused environment.

You’ll work directly with our lead engineer and cross-functional partners including design and clinical teams, building AI-powered personalization and robust blood-testing infrastructure for UK and international users.

Qualifications

• 5-8 years of backend experience with strong fundamentals.
• Experience at a startup or scale-up and true ownership.
• Ability to discuss end-to-end systems and trade-offs.
• Track record of shipping reliable systems.
• Comfort with AI tools in workflow.
• Judgement in ambiguous situations.

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 for personalization at scale.
• Improve reliability, observability, and foundational systems.
• Collaborate with product, design, and clinical teams.

Skills

Backend architecture

End-to-end ownership

Scalability

AI tooling awareness

Problem-solving

Tools

TypeScript/Node.js

Go/Python

Job description

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