About ONE FIIT
ONE FIIT is the 'fitness operating system' that connects brands, gyms, and trainers with their communities as part of its mission to make exercise a lifelong habit for everyone. As an all-in-one solution for digital and in-person group training, ONE FIIT powers premium fitness experiences for leading brands including HYROX, FIIT, Huawei, Women's Health, Men's Health, and Nespresso, and for companies such as The Gym Group, IHG, Serco Leisure, Westfield Health and Cortland Living. Whether through our No.1 rated connected training app FIIT, hybrid studio/gym app, trainer portal (or all three), gyms, hotels, residences, and brands can seamlessly acquire, engage, and grow their communities. In 2025, FIIT was named one of the Most Innovative Fitness and Wellness Companies by Athletech News.

What do we want?
We're building the fitness platform of the future — and we're looking for a Fullstack JavaScript Engineer to join our team. You'll work across our modern JavaScript stack, from backend GraphQL APIs to greenfield frontend micro-apps, helping us ship high-quality features at pace.

What does that look like?

• Design, build, test, and deploy new features from idea to production
• Collaborate with product managers, designers, and fellow engineers to deliver solutions quickly
• Embrace and utilise AI-powered developer tools like Claude Code and Cursor to optimise workflow, testing, and documentation
• Take ownership of releases — we ship code daily!

What you'll need (essential)

• Strong knowledge of the fullstack JavaScript ecosystem: React, Node.js, and TypeScript
• Experience with GraphQL and SQL (PostgreSQL)
• Ability to contribute quickly in a fast-paced environment
• Great English communication skills, both within engineering and with non-technical colleagues
• A growth mindset — eager to learn and adapt on the job

Other desirable but not essential skills

• Tailwind
• Testing frameworks (Jest)
• Component libraries (Storybook)
• Prisma
• Docker / containerisation experience

What's in it for you?
As well as working on a revolutionary greenfield project, alongside an amazing team, we've spent a lot of time thinking about how to look after our employees. We've centred our benefits package around 4 core pillars and we think you'll agree we've done pretty well.

The money

• Competitive salary depending on experience
• Company performance-based bonuses paid each quarter
• Equity options
• Pension

Health & Wellness

• £200 per quarter to spend on whatever wellness means to you — PT, gym membership, massages
• A free FIIT device and subscription, and the chance to test out all of the new classes and concepts
• Private health and dental insurance with Bupa, plus a GP service, eye tests and flu jabs
• Free access to coaching and counselling sessions through the Inside Out platform, plus monthly seminars
• £350 to set up your new home working station

Personal Development

• £1,000 p.a. to focus on your professional development
• Clearly defined levels within the business, so there's always the opportunity to progress in your role
• Quarterly reviews, with clear OKRs to keep everyone aligned and on track
• Personal development plans so you can shape where you want to go
• Company-wide training
• Management training (if you look after a team)

Work/life balance

• Hybrid working model — flexible on when you come into the office
• When you do come in, it's a very cool place to be near the Olympic Park in Stratford, with unlimited drinks and snacks
• Unlimited holiday (yes, you read that right)
• Family-friendly policies including maternity, paternity, adoption and parental leave
• Monthly team days where the whole company gets together and has some fun
• £200 p.a. for new hobbies — we'd love you to try out something new

Our Values

• Always improving — you'll be learning, curious, and embrace giving and receiving constructive feedback.
• Grit to deliver — startup life is a rollercoaster; you'll execute at pace and take accountability.
• The team is greater than the individual — we include everyone, value diversity, and communicate openly.

Location
FIIT is based at the Here East campus in the Queen Elizabeth Olympic Park, within easy reach of two major stations, with a free shuttle bus and well connected to cycle paths.

At FIIT, we're committed to hiring diversely. Having employees from diverse backgrounds brings a wealth of perspectives and experience to our team. We recognise that minority candidates face a unique set of barriers when accessing opportunities. We've taken care to craft a hiring process where candidates are judged on their unique talent and aptitude, not their identity.