Senior Backend Engineer
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 a vast set of simple and affordable business tools to help them start, run, and grow their businesses. Today, over 4 million businesses in 36 markets rely on SumUp as their financial partner to manage payments, finance and customer relationships.
About the Team
You'll join the
Sell Online Tribe, the group shaping how merchants bring their businesses to life online. We design and build tools that help millions of entrepreneurs, from barbers to bakers, sell their products and services anywhere. Our focus is on Online Store and Bookings, two products at the heart of SumUp's ecosystem. Together, they give merchants the power to manage appointments, showcase their offerings, and get paid-all from their phones.
We're a cross-functional team of Product Managers, Designers, and Engineers who move fast, collaborate openly, and care deeply about crafting beautiful, performant mobile experiences. As part of this team, you'll help us expand into new verticals, close the feature gap, enabling us to position our product as a complete and competitive solution for small merchants, and make digital selling effortless for small businesses everywhere.
What You'll Do
Design, build, and maintain scalable backend systems supporting SumUp's Bookings product
Collaborate with frontend and mobile engineers to deliver new features and improve APIs across web, iOS, and Android
Participate in technical planning, code reviews, and design discussions to ensure clean, testable, and maintainable code
Continuously optimise performance, ensure observability, and uphold our high reliability standards
Actively contribute to shaping the technical roadmap for the Sell Online platform
You'll Be Great for This Role If
You have 5+ years of professional backend engineering experience
You're fluent in Kotlin (or Java) and have deep experience with Spring Boot
You've worked with PostgreSQL, Kafka, Docker, Kubernetes, and AWS
You understand RESTful APIs, distributed systems, and event-driven architectures (e.g. CQRS, Event Sourcing)
You bring experience with CI/CD pipelines, GitHub Actions, and observability tools like Grafana or Honeycomb
You thrive in collaborative teams, enjoy mentoring peers, and care about delivering real value to merchants
(Nice to have) Familiarity with gRPC, Protobuf, or performance optimisation at the backend/database level
Why You Should Join SumUp
Opportunity to work from our vibrant Warsaw office in the Hala Koszyki. This involves a hybrid 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
Fitness support: work out on-site at our gym or explore the city using the Multisport Card, subsidised by SumUp for access to sports facilities across Warsaw
Commitment to well-being: access health insurance coverage for you and your family, plus life insurance to further protect your peace of mind
PPK (Employee Capital Plan): grow your savings with joint contributions from SumUp and the State
Generous time off: enjoy 26 days of paid leave plus public holidays and special leave days
Break4me: 1-month sabbatical after 3 years of service
Referral Bonus: earn additional rewards by referring talented individuals to join the SumUp team
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.