Senior Full Stack Engineer

The SuperApp squad owns parts of the merchant experience across Web, Android, iOS and the flows that millions of small business owners use every day to run and grow their businesses. As our dedicated full stack web engineer within the squad, you'll own this space entirely, shaping technical direction, driving feature parity for SumUp's web experience. If you want real ownership, a broad scope, and work that lands directly in the hands of millions of merchants, this is the role. WHAT YOU'LL DO: * Own and develop core web dashboard features including the first-time user experience, home screen widgets, quick actions, tools section, and communications centre * Build and maintain the backend services that power these flows, ensuring a seamless and consistent experience across web and mobile * Work closely with iOS and Android engineers, product managers, and designers to shape cross-platform solutions and contribute to technical direction * Lead the design and refinement of technical solutions — writing clear documentation, making architectural decisions, and communicating progress to stakeholders * Be an active contributor to the web chapter and the broader engineering community at SumUp WHAT WE'RE LOOKING FOR: * Strong, proven experience with React.js and TypeScript, building scalable, maintainable applications in a production environment. * Comfortable working across the stack, with experience building backend services or REST APIs, Go is a plus, but Node.js or similar is equally welcome. * Ability to navigate and refactor complex codebases with a focus on clean, durable code and solid system design. * Experience working in cross-functional teams alongside product managers and designers, with a strong sense of ownership and comfort with ambiguity. * A product mindset, thinking about the merchant experience, not just the code, and connecting technical decisions to real business outcomes. WHY YOU SHOULD JOIN SUMUP: * 🌎 Opportunity to work with SumUppers globally on large-scale fintech products used by millions of businesses worldwide, from our Berlin office. This involves an office-first setup * 🌈 Commitment to Diversity and Inclusion: be part of a workplace that values and promotes diversity, fostering an inclusive environment where everyone's perspectives are respected and embraced * 🚀 Enrolment onto our Virtual Stock Option programme: you will own a stake in SumUp's future success * 📚 A dedicated annual L&D budget of €2000 for your individual development, which can be used to attend conferences and/or advance your career through further education * 💶 A corporate pension scheme where we match up to 20% of your contributions * 🏖️ Generous time off: enjoy 28 days of paid leave plus public holidays and special leave days * 🏋️ Numerous other benefits such as Urban Sports Club subsidy, Kita placement assistance, subsidised office lunches * 🌴 Break4me: 1-month sabbatical after 3 years of service * 🔗 Referral Bonus: earn additional rewards by referring talented individuals to join the SumUp team ABOUT SUMUP Be empowered to do more that matters. At SumUp, we're on a mission to empower small businesses across the globe by providing simple and affordable tools that allow them to thrive. Today, over 4 million businesses in 37 markets rely on SumUp as their financial partner to manage payments, finance and customer relationships. Our commitment to small businesses is reflected in our diverse team of over 3,000 SumUppers from over 90 nationalities, united by global collaboration and an innovative mindset. Our core values lay the foundation for who we are and what we stand for, shaping our work culture and driving our success. We foster inclusivity and a continuous learning culture, providing a safe space for personal and professional growth. Our differences make us unique and strong as we strive to create an environment where everyone belongs and feels supported, no matter how they identify. SumUp is proud to be an Equal Employment Opportunity employer, actively seeking and embracing diversity in our workforce. We don't make hiring or employment decisions based on race, colour, religion or religious belief, ethnic or national origin, nationality, sex, gender, gender identity, sexual orientation, disability, age or any other basis protected by applicable laws or prohibited by company policy. Our commitment extends beyond recruitment to creating a safe and respectful workplace where harassment of any form is strictly prohibited. Discover more about our culture and opportunities on our careers website, and follow our journey on LinkedIn, Instagram, and TikTok. Job Application Tip We recognise that candidates feel they need to meet 100% of the job criteria in order to apply for a job. Please note that this is only a guide. If you don’t tick every box, it’s ok too because it means you have room to learn and develop your career at SumUp.

ABOUT THE OPPORTUNITY ABOUT THE OPPORTUNITY We are looking for a Senior Full-Stack Engineer who will take ownership of crucial engineering activities at Kadmos. As a regulated salary payment provider in the shipping industry, we are building secure, reliable, and scalable financial solutions that empower seafarers and shipping companies worldwide. You will play a central role in shaping both the backend infrastructure and frontend experience of our platform, driving innovation in a highly regulated environment. WHAT YOU CAN EXPECT * Own the full stack. You will be responsible for developing and maintaining core backend systems and frontend applications, building reusable libraries, implementing complex financial components, and integrating with external service providers. * Work with independence. You’ll be trusted to take full ownership of your responsibilities, while collaborating closely with product, compliance, and engineering teams. * Impact at scale. You will contribute directly to a platform serving the global shipping industry, with the opportunity to design systems that handle secure financial transactions and deliver exceptional user experiences. * Collaborative environment. We value diversity, transparency, and teamwork. You’ll join an open and supportive culture where everyone’s input matters. WHAT YOU BRING ALONG * 5+ years of professional experience in full-stack development with Java Spring Boot and React. * Master’s degree in Computer Science, Mathematics, or Physics. * Backend Proficiency: Expertise in Java with strong knowledge of Spring Boot and modern frameworks, SDKs, API standards, and libraries. * Frontend Proficiency: Expertise in React with a strong emphasis on TypeScript. Experience with Redux, React Query, styled-components, MUI Component Library, or similar tech stack. * Extensive hands-on experience in developing scalable and testable high-quality solutions in an agile environment. * Solid experience with unit, integration, and performance testing (JUnit, Spock, Testcontainers on the backend; React Testing Library and Cypress on the frontend). * Strong understanding of building secure, reliable, and scalable systems, ideally in a regulated or financial services context. * Proactive, ambitious, and collaborative mindset with a track record of delivering high-quality solutions. * Fluency in English. WHY US * 🌱 Opportunity to work in a company with direct social impact * 💰 Attractive compensation * 🇺🇦 Open & International environment * 🏛️ Fantastic location in the heart of Berlin & flexible WFH policy * 🥘 Free lunch at the office * 💻 Latest equipment, to ensure you have everything needed ABOUT THE COMPANY Kadmos is on an ambitious mission to revolutionise salary payments to migrant workers. The Berlin-based startup was founded in 2021 by MIT graduates Justus Schmueser and Sasha Makarovych to bring fintech, low margins, and transparent FX to industries riddled with opaque mark-ups, kickbacks, and physical cash transactions. Backed by renowned VCs Addition and Atlantic Labs, Kadmos has raised more than $39 million since 2021. The company intends to use the funding for expanding across industries and further accelerating product development. For more information, visit https://www.kadmos.io/