Staff Backend Engineer

Worky; Greater London; Hybrid; GBP 120,000 - 180,000; Full time

Job summary

Do Health is recruiting a Staff Backend Engineer in London, hybrid (3 days/week in person). As part of the founding team inside Voy, you’ll own major backend features end-to-end, shape architecture and scale our blood testing infrastructure for the UK and beyond.

You will build production AI systems for personalization, improve reliability and observability, and work directly with product, design and clinical teams with no layers between you and the work.

Qualifications

• 7-9 years of backend experience with strong fundamentals.
• Experience at a startup or scale-up where you owned things.
• Architectural thinking and ability to discuss end-to-end systems.
• Track record of shipping reliable infrastructure.
• Comfort with making judgments in ambiguous situations.
• Confident use of AI tools in workflow as a multiplier.

Responsibilities

• Own major backend features end-to-end; design, build, ship, monitor, iterate.
• Shape architecture and make technical decisions.
• Scale blood testing infrastructure across the UK and internationally.
• Build production AI systems for personalization.
• Improve reliability, observability and foundational systems.
• Collaborate directly with product, design and clinical teams.

Skills

Backend development

System design

Startup/scale-up experience

AI tooling usage

Observability

Tools

TypeScript / Node.js

Go / Kotlin / Python

Job description

Staff Backend Engineer

Do Health - London, Hybrid (3 days/week in person)

Why this role exists

We're hiring a Staff Backend Engineer as a part of the founding team 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 (£600M+ 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 actually do

• Own major backend features end-to-end - design, build, ship, monitor, iterate. Not "contribute to" - own.

• Shape architecture. 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.

The kind of engineer this works for

You'll fit if you have:

• 7-9 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

Why this might be the right move

• Genuine equity in a product with real upside, not lottery-ticket equity at a company that may never exit

• Startup velocity with grown-up backing - Voy isn't going anywhere, so you're not betting your mortgage on Series A survival

• A product that matters. Preventative health is one of the few areas where building software actually changes outcomes, not just engagement metrics.

• A high technical bar from day one. You're not joining a team that needs convincing to do things properly

• Direct access to leadership - your work, your decisions, your name on them.

Practical details

• Location: London

• Working pattern: Hybrid, ~3 days per week in person

• Compensation: Competitive - happy to discuss bands early in the process

• Process: Intentionally short. Hiring manager interview, technical conversation, team chat. We move fast for the right person.