Company Description

Joy is a proactive healthcare company. We find the patients who are about to get worse before they get worse & connect them to the services that change their trajectory. Then we prove it worked. That last part is the hard part but it's also the interesting part.

We work with NHS commissioners, GPs & local authorities across the UK. Our platform identifies rising-risk patients from complex, messy, real-world health data, matches them to interventions & measures whether those interventions actually shifted outcomes, to prove genuine, demonstrable health impact.

Why This Role Exists

Joy is at a turning point. We have a platform that works, customers who rely on it & patients who benefit from it. But the technology underneath was built for the stage we were in, not the stage we're heading to.

We want to transform our current stack (.NET/WPF, Rails, Azure) into something built for the next stage (Rust, Python, React, AWS). We need someone who can hold both worlds. Keep the current platform alive & improving while architecting & building the next one. Not in theory. In production.

What this role is

This is a transformation role. You're not maintaining a legacy system. You're building its replacement while keeping it running. You'll work directly with our Head of Engineering as his technical right hand. Sharing architectural thinking, owning the critical path & bringing a growing team of engineers on the transformation journey.

In practice, you will:

• Own the migration of JoyConnect from .NET/WPF to Rust, drastically reducing the product's resource footprint

• Maintain & stabilise the existing .NET/WPF codebase while the migration is underway. You don't have to love WPF, but you need to be competent enough in .NET to keep it healthy

• Support existing Rails infrastructure during its transition period. We're not looking for a Rails expert, but you should be comfortable enough to ship fixes & keep things stable

• Build & evolve Joy's Python-based algorithms for patient identification, risk stratification & outcome measurement

• Own & iterate on Joy's AI-powered product features built on OpenAI & Anthropic APIs. You should be comfortable designing, building & shipping LLM-integrated systems

• Drive adoption of AI tooling across the engineering team. Copilot, Claude & whatever comes next. Not as an experiment but as how we work

• Shape the DevOps capability in-house, reducing dependency on external providers

• Grow the team. Set high standards & create an environment where strong engineers want to stay & get better

• Make technical decisions that serve business objectives: conversion rates, patient outcomes & commissioner confidence. Not architectural elegance for its own sake

Who thrives in this role

You've done this before. Maybe not this exact stack, but the shape of the problem is familiar: a growing company with a product that works, technology that's showing its age & a team that needs someone to draw the line from here to there.

You're the kind of engineer who sees a .NET/WPF codebase & thinks "I can keep this alive" not "this is beneath me." You see Rust & think "this is where I want to be spending my energy." You understand that both of those things need to be true at the same time, for months, maybe longer. & you're fine with that because you've navigated transitions before & you know the craft is in the overlap.

You don't wait for permission. You see a bottleneck, you fix it. You see a better way to structure something, you propose it with evidence. You disagree respectfully & directly. You treat "that's how we've always done it" as a smell, not a reason. If you've ever been described as "opinionated but usually right," keep reading.

You should talk to us if you

• Have 10+ years of engineering experience, with at least a few of those leading teams & owning architecture

• Have strong Rust experience or deep conviction & demonstrable progress toward Rust as your primary language

• Are comfortable in Python for data-heavy, algorithmic work

• Have enough .NET experience to maintain & stabilise a WPF codebase without needing hand-holding

• Have led or been central to a major platform migration (language, framework or infrastructure level)

• Have hands-on experience integrating LLMs into production systems: prompt engineering, API orchestration, evaluation & guardrails. The real stuff, not a hackathon demo

• Treat AI tools as part of your daily workflow & have opinions about how engineering teams should adopt them

• Can context-switch across languages, frameworks & problem domains without losing depth

• Can articulate trade-offs to non-technical stakeholders without dumbing things down or hiding behind jargon

• Have a track record of hiring & developing strong engineers

• Care about outcomes. If the architecture is beautiful but conversion hasn't moved, you consider that a failure

Nice to have

• Rails experience (we have it in the stack, it's not the future, but someone needs to mind it during the transition)

• Azure & AWS experience (we're on Azure today, the future cloud home is an open conversation)

• DevOps skills or experience building DevOps capability within an engineering team

• React experience for our UI layer

• Healthcare or NHS experience (genuinely not required, but if you have it, great)

You don't need to

• Love WPF. You just need to be willing to keep it alive while you build what replaces it

• Be a data scientist or ML engineer. We need someone who can build with AI, not build AI from scratch

• Live in the UK. We're fully remote & async-friendly. We care about overlap with UK hours for key meetings, not about your postcode

• Have a degree. We care about what you've built & how you think

What you'll get

• A genuine transformation. Not a "modernisation initiative" that never ships, but a real migration with executive backing & a clear destination

• A product that actually matters. We measurably improve patient health outcomes

• A technical landscape that's genuinely challenging, not just enterprise CRUD

• Direct influence over architecture, team culture & technical direction

• A leadership team that respects engineering & doesn't treat it as a cost

• The freedom to do your best work, wherever you do it from