Senior Backend Engineer

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 mobile experiences. As part of this team, you’ll help us expand into new verticals, close the gap between web and mobile, and make digital selling effortless for small businesses everywhere.

About the role 

You will be working on some of SumUp's biggest merchant-facing online products as part of the Bifrost team. You'll contribute to maintaining and growing critical products like Payment Links, Virtual Terminal, and Unified Gift Cards, while also working on integration products that provide essential features used across many other SumUp products.

You're a developer who values reliability, collaboration, and continuous improvement. You bring backend expertise and thrive in a high-impact environment where your work directly supports merchant success and team scalability.

What you'll do

• Provide redundancy for the maintenance and continuous growth of some of the biggest online products in SumUp
• Contribute to the implementation, growth and integration of Online Checkouts throughout SumUp
• Actively participate in planning and reviewing sessions on quarter and sprint levels by providing constructive feedback and estimations
• Monitor existing services and make necessary fixes to ensure platform reliability
• Implement new features with maintainable and testable code
• Optimize and improve application performance for scalability
• Participate in code reviews to maintain high code quality standards

You'll thrive in this role if:

• You have 5+ years experience in backend engineering with Golang
• You have a strong understanding of fundamental system architecture, design principles, data modeling, and API design
• You have strong experience with distributed and fault-tolerant systems
• You have user-level experience working with AWS and Kubernetes
• You have good knowledge of Kafka & Postgres
• You're passionate about building products that help small businesses succeed and grow

Why You Should Join SumUp (Warsaw) 🇵🇱

🌎 Opportunity to work , from our vibrant Warsaw office with inspiring art-filled lounges and a skyline terrace in the Mennica Legacy Tower. 

🌈 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 VSOP program: you will own a stake in SumUp’s future success 

🚴 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