(Senior) Backend Engineer - Golang

About the team: We are the Merchant Risk Intelligence team within SumUp’s Risk & Compliance tribe. We build systems that help protect SumUp and its merchants from fraud while supporting reliable, compliant business growth. Our team combines software engineering, machine learning, data science, product management and risk expertise. You will join a multidisciplinary group currently working across backend services, data products and AI-powered solutions. The team is growing its software engineering capabilities to develop Sentinel, our entity-level investigation and actioning framework, and to support broader risk and compliance use cases. You will bring dedicated Golang expertise to the team while also contributing to Python-based services and AI-agent initiatives. We value pragmatic engineering, thoughtful collaboration and the ability to balance delivery speed with security, reliability and long-term maintainability. What you’ll do: Develop new functionality and support existing services across the tribe’s codebase, primarily using Go Contribute to the continued development of our in-house merchant risk decision framework, taking it beyond its MVP and enabling new fraud prevention, risk and compliance use cases. Design, build and maintain reliable distributed systems and backend services. Work closely with product managers, data scientists, machine learning engineers, fraud strategy teams and operational stakeholders to turn complex problems into practical solutions. Help shape technical direction, service boundaries and system design decisions across the team. Contribute to Python projects, including AI-agent initiatives, as you build a broader understanding of the team’s systems. Participate in code reviews, testing, monitoring and continuous improvement of production services. Use AI-assisted development tools thoughtfully to deliver meaningful features faster without compromising code quality, security or maintainability. Be open to participating in an on-call rotation as the team’s production responsibilities and support model evolve. You’ll be great for this role if you have: Professional experience developing software with Go/Golang Experience building and operating distributed systems and backend services Strong system design skills and an understanding of reliable, maintainable software architecture. Experience working with Kubernetes and Kafka Working knowledge of Python and an interest in contributing to Python-based products or AI/agentic development Experience using AI-assisted tools as part of your software development workflow Experience working in agile, cross-functional teams and collaborating with stakeholders beyond engineering A pragmatic, outcome-focused approach: you know how to define a valuable MVP, make sensible trade-offs and improve solutions iteratively A collaborative mindset and the confidence to challenge ideas constructively while remaining open to feedback Motivation to learn about fintech, fraud prevention, risk and compliance domains Why you should join SumUp: 🌍 Opportunity to work with SumUppers globally on large-scale fintech products used by millions of businesses worldwide, from our Sofia office. This involves an office-first setup 🧑‍🔬 We take learning and experimentation seriously with Hack Days every second Friday, and entire global Hack Weeks . 🌈 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 📚 A dedicated annual L&D budget of €2,000 for attending conferences and/or advancing your career through further education 🚀 Enrolment onto our VSOP program: You will own a stake in SumUp’s future success 🏖️ Generous time off: 25 days of paid leave, plus one extra day per year of service (up to 35), along with public holidays and special leave options 🔄 30 Days Sabbatical: Enjoy the unique opportunity to take a well-deserved break with our 30 days…