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- Tasks: Lead the development of our cutting-edge fitness app and enhance user experience with innovative features.
- Company: Join MARCHON, the UK's premium performance-lifestyle brand transforming fitness and wellness.
- Benefits: Enjoy 22 days holiday, a birthday off, pension contributions, and a £400 annual gift card.
- Why this job: Make a real impact in a fast-paced environment while shaping the future of fitness technology.
- Qualifications: Proven experience in digital product development and expertise in Swift, Node.js, or React.
- Other info: Collaborate with a high-performing team and enjoy excellent career growth opportunities.
The predicted salary is between 36000 - 60000 £ per year.
MARCHON is the UK's premium performance-lifestyle ecosystem, one brand that helps driven people train, fuel and dress for a life without limits. World-class coaching sits at the centre, backed by certified performance nutrition and movement-ready apparel, all amplified by our beacon gyms. Founded by ex-England rugby player and CEO Ollie Marchon, the company has grown from a single HQ club to a true omni-channel offering: the Train app, a fast-scaling supplement line, and physical hubs that bring the experience to life.
We're still small enough that every new teammate leaves fingerprints on the product, yet the momentum is real. Our 2026 plans are ambitious to say the least, as we make a step-change in evolving our ecosystem between training, supplements and apparel. If you care about high standards, straight talk and making a visible impact, you'll feel at home here. Join us while there's still room to shape the journey.
The Role
We are looking for a Senior Engineer. You'll help scale the next generation of the UK's leading fitness app - powering proprietary performance scores, intelligent training recommendations, and social competition features that take us 10x beyond today. This is an opportunity to join a high performing team, driving end-to-end product development in a highly autonomous, async environment to build extraordinary tools that unlock our users' fitness and performance potential.
Key Responsibilities
- End-to-end development of our apps, from shaping product requirements to shipping high-quality, scalable features all the way from client to server.
- Design and maintain a robust, modular architecture that allows us to build and test new functionality fast.
- Build and evolve integrations with wearables such as Apple Watch, Garmin, Cronos, and other health/fitness data sources.
- Design, ship, and continuously improve applied AI capabilities across the product - building production-ready LLM-powered features, orchestration layers, evaluation flows, and internal tooling that directly enhance user experience and team efficiency.
- Implement performance, reliability, and analytics foundations, including intelligent recommendations, workout tracking, and data ingestion.
- Own code quality and technical standards, driving testing, refactoring, documentation, and scalable engineering patterns across the codebase.
Experience & Skills
- Proven experience building high quality digital consumer products, ideally in fast-moving/start-up environments.
- Deep expertise in at least one of our core technologies - Swift/SwiftUI, Node.js, or React/React Native - with the openness and eagerness to learn new technologies.
- Hands-on experience building production features with LLM APIs - including structured output, tool-calling, embeddings, retrieval pipelines, and prompt design - with a focus on reliability, performance, and real user impact.
- Experience working with AI-powered product features, including LLM integration, prompt design, embeddings, or vector-search workflows.
- Strong understanding of scalable application architectures, including modular codebases, efficient data flows, and performance tuning.
- Comfort working across the stack and collaborating closely with product and backend teams to shape APIs, data models, and user-facing functionality.
- Ability to operate autonomously, breaking down ambiguous problems and making pragmatic technical decisions.
- A product-driven mindset, showing empathy for users and an ability to translate real-world needs into thoughtful, robust features.
- Hands-on experience integrating wearable or health data sources, such as Apple Health/Watch, Garmin, Cronos, or similar ecosystems is a huge bonus.
22 days holiday + 8 bank holidays + Your birthday off. Pension contributions. "Starter Pack" of all things MARCHON. £400 gift card each year for MARCHON Supplements & Apparel. Year-round staff discount on Supplements & Apparel. Free membership to all MARCHON gyms. Full access to MARCHON Online training & nutrition platform.
Senior Engineer employer: MARCHONTM
Contact Detail:
MARCHONTM Recruiting Team
StudySmarter Expert Advice 🤫
We think this is how you could land Senior Engineer
✨Tip Number 1
Get to know the company inside out! Research MARCHON's values, products, and culture. This way, when you chat with them, you can show you're genuinely interested and ready to contribute to their mission.
✨Tip Number 2
Network like a pro! Connect with current employees on LinkedIn or attend industry events. A friendly chat can sometimes lead to insider info or even a referral, which can give you a leg up in the hiring process.
✨Tip Number 3
Prepare for the interview by practising common technical questions related to your expertise. Since MARCHON is all about high standards, showing off your skills confidently will help you stand out from the crowd.
✨Tip Number 4
Don’t forget to apply through our website! It’s the best way to ensure your application gets seen by the right people. Plus, it shows you’re serious about joining the MARCHON team!
We think you need these skills to ace Senior Engineer
Some tips for your application 🫡
Show Your Passion: When you're writing your application, let your enthusiasm for fitness and technology shine through. We want to see how your interests align with our mission at MARCHON, so don’t hold back on sharing what drives you!
Tailor Your CV: Make sure your CV is tailored to the Senior Engineer role. Highlight your experience with the core technologies we use, like Swift or Node.js, and any relevant projects that showcase your skills in building high-quality digital products.
Be Clear and Concise: Keep your application clear and to the point. We appreciate straightforward communication, so avoid jargon and focus on what makes you a great fit for the team. Remember, less is often more!
Apply Through Our Website: We encourage you to apply directly through our website. It’s the best way for us to receive your application and ensures you’re considered for the role. Plus, it shows you’re keen to join the MARCHON family!
How to prepare for a job interview at MARCHONTM
✨Know Your Tech Inside Out
Make sure you’re well-versed in the core technologies mentioned in the job description, like Swift/SwiftUI, Node.js, or React/React Native. Brush up on your experience with LLM APIs and be ready to discuss specific projects where you've implemented these technologies.
✨Showcase Your Problem-Solving Skills
Prepare to talk about how you've tackled ambiguous problems in the past. MARCHON values autonomy, so think of examples where you made pragmatic technical decisions that had a real impact on the product or user experience.
✨Understand the User Experience
Demonstrate your product-driven mindset by discussing how you empathise with users. Be ready to share insights on how you’ve translated real-world needs into robust features, especially in the context of fitness apps or health data integration.
✨Be Ready for Technical Challenges
Expect some technical questions or challenges during the interview. Practice coding problems related to scalable application architectures and modular codebases. This will show that you can not only build but also maintain high-quality digital products.
