Senior Full Stack Engineer (React & Java)

Employment: Full-time Experience: Mid-Senior level Senior Full Stack Engineer (React & Java) We build and operate Connect, a SaaS platform for the beauty & wellness industry that helps entrepreneurs run their businesses more effectively, built by Treatwell. Our web products are used daily by tens of thousands of people across 13 European countries. Our teams own their areas from initial idea and design through deployment and operations. We focus on writing maintainable, scalable code while balancing legacy and modern technologies. We encourage engineers to experiment with new ideas, learn from mistakes, and improve our systems continuously. You will be responsible for: Take ownership of features across the stack, from database schema and backend services to the UI, from design through deployment and operations. Pair with engineers, designers, and PMs to ship features every cycle, iterating based on real usage and feedback. Participate in design and code discussions, making trade-offs and decisions that affect the product and the team. Maintain a strong focus on automated testing, applying the testing pyramid to ensure unit, integration, and end-to-end coverage. Improve observability across services and the frontend by adding metrics, dashboards, and alerts with tools like Datadog, Sentry, and web vitals, so issues are caught before they impact users. Design and build backend services and APIs in Java and Spring Boot, including event-driven flows with RabbitMQ. Own your services end-to-end, with a DevOps mindset, from architecture through deployment and operations. Validate ideas with data: instrument your work, measure its impact, and use evidence to decide what to scale. Be an active part of the Engineering Guild, collaborating with other engineers to share ideas, improve standards, and tackle cross-team challenges. Lead technical discussions about trade-offs in features, architecture, and UX, helping the team make informed decisions that balance product goals and engineering constraints. Navigate a hybrid codebase, balancing work between legacy systems and modern React/TypeScript. Build internal tools that help operations and support teams move fast without creating risk About you 7+ years of software development experience, with a strong focus on modern web frontend and hands-on experience building backend services. You take responsibility for the code you write and the areas you own, spotting bugs, performance issues, or UX gaps, and fixing them proactively without waiting for direction. You own features end-to-end, from database schema to UI, without needing a handoff. You have a product mindset. You think about the person using what you build, ask why before how, and push back when something doesn't make sense. You think in systems and trade-offs, and you look for the upstream cause, not just the downstream symptom. You are data-driven. You instrument your work, measure impact, and use evidence to make decisions. You actively leverage AI tools in your daily development workflow, viewing them as force multipliers for productivity, code quality, and problem-solving. You are comfortable with ambiguity in complex domains and can make progress without getting paralysed. You have sharp product thinking and a focus on UX, paying attention to the little things: edge cases, empty states, and error handling. You have excellent English communication skills and can explain complex technical ideas clearly to engineers, designers, and non-technical stakeholders. You are comfortable working with remote and co-located teams, and you are structured, analytical, and highly collaborative. Our stack Frontend: The application originally grew as a Backbone-based product, served through Node/Express with EJS templates, and there are still important areas of the product that work this way today. The team is migrating the frontend toward React and TypeScript, page by page and feature by feature. In practice, that means most new development now happens in the modern React/TypeScript stack, using tools and patterns such as React Query, Storybook, Jest, and Cypress, while some work still involves the legacy Backbone codebase and the integration layer between old and new parts of the app. Backend: Java, Spring Boot, RabbitMQ, PostgreSQL, MS-SQL Infrastructure: Kubernetes, GitLab CI/CD, AWS, Datadog Mindset: DevOps, DDD, event-driven architecture We’ll treat you with: 28-days holiday, plus bank holidays Monthly £/€40 Treatwell vouchers so you can treat yourself too Mental health support through our partnership with Open-Up 100% remote position Market-specific benefits that will be discussed in the interview process Equal Opportunities Treatwell is an 'Open to All' employer and warmly welcomes everybody to the team. We are committed to making reasonable adjustments to the recruitment process as required. Please add any adjustment requests to your application.