React JS Full Stack Senior Developers, in London

Senior Full Stack Engineer (London)About FreshaFresha is the leading AI-powered operating system for the global beauty and wellness industry, giving businesses everything they need to run smarter, grow faster and build stronger client relationships.In May 2026, Fresha secured an $80M growth investment from KKR at a valuation of $1B, officially reaching unicorn status and bringing total funding raised to $285M. Already profitable, Fresha is using this investment to accelerate global expansion and drive the next generation of AI and product innovation.Our mission is simple: help beauty and wellness businesses grow by giving them the technology they need to attract clients, manage their operations and run their business in one place.Role OverviewSenior Full Stack Engineer | The Bower, 207-211, Old St, Tower, London EC1V 9NR | Four days in office, Wednesdays remoteYou'll join a cross-functional product team and report to its Team Lead.Full stack here means you own a feature the whole way down: the React and TypeScript screens people use, the GraphQL layer in between, and the services behind it. Your change usually reaches production the same day you write it, behind a feature flag. The team that builds a service looks after it, including a shared on-call rota.We're also changing how engineering gets done here. It isn't finished, and you'd be helping to shape it rather than inheriting it. Design it, build it, test it, ship it, and look after it once it's live.Build the UI: Implement new functionality and interfaces in our web frontend, against a custom design system, and in the native apps when a piece of work reaches them.Design and document APIs: GraphQL and gRPC APIs that your own team and other teams will build on, built to be used by people who won't ask you first.Ship most days: Work across services: You'll plan and ship changes across several services at once.Product, Design, Frontend, Infrastructure and Mobile, from the first conversation through to release.Find the bottlenecks, fix the bugs, and keep an eye on performance and quality.Our architecture and our engineering practices aren't fixed. Our stack: the web frontend is React and TypeScript on a custom design system, talking to the backend through a federated GraphQL layer. Services are written in Ruby, Elixir and TypeScript, with Kafka for events, gRPC or JSON for synchronous calls, Postgres, and everything running in Kubernetes. Domain-driven design is at the heart of how we work: we build fast, but we think about the bounded context first. We're partway through breaking our Ruby/Elixir monoliths into services. Our mobile apps are native, Swift on iOS and Kotlin on Android, and the APIs you write serve them too. You don't need Swift or Kotlin on day one, but you will work across them as the work requires.What We're Looking ForExperience: 5+ years building and running product software in production.You're strong in either the frontend or the backend and you can hold your own in the other. Frontend: Commercial experience with React and TypeScript, and with building interfaces that hold up. Comfortable with CSS, including animation, and with the usual JavaScript build tooling.We don't expect Ruby or Elixir on day one, but we do expect you to pick things up fast.You design for it rather than finding out later.You're at ease shipping behind flags and watching a change land. AI in your workflow: You use AI coding tools day to day and have a clear view of where they help and where they don't. You're happy building your own workflow rather than waiting for one, and you review what comes back before it ships.Pragmatic: You care about the right tool for the job more than any particular stack, and you've worked in more than one style of language.Native mobile experience is a bonus rather than a requirement, but we do expect engineers to pick up what a piece of work needs.Ownership: The tooling, data and permissions to run what you build, and a say in the technical direction of your area.You see a feature from the screen a salon owner taps to the service that handles it. We do not discriminate based on race, colour, religion, sex, sexual orientation, age, marital status, gender identity, national origin, disability, or any other applicable legally protected characteristics in the location in which the candidate is applying.We may use artificial intelligence (AI) tools to support parts of the hiring process, such as reviewing applications, analyzing resumes, or assessing responses. If you would like more information about how your data is processed, please contact us.