(Senior/Mid) Software Engineer, Golang - Payments Platform

SumUp enables businesses to get paid easily, process orders quickly, sell online instantly and manage their money more efficiently. We create the tools businesses need to make their business and their customer experience thrive. The payments processing platform, consisting of other sub-platforms, has powered SumUp’s global business for more than 10 years now. It’s developed in Sofia by the Payments Tribe, composed of several teams (squads). Each squad is cross-functional, autonomous and co-located, working on its part of the platform end-to-end. We are scaling and improving existing products, while developing new ones - an exciting time to join. You would make an impact by improving and co-creating our existing and new microservices architecture platforms, solving scaling and new development challenges. Scalability and high availability are among our focus areas. What you’ll do Design and evolve systems that process millions of transactions reliably and at scale Build and maintain backend services in a microservices architecture Contribute to API design for internal services and external integrations Write clean, maintainable, and scalable code with strong test coverage Participate in architectural discussions and drive technical decisions Collaborate closely with engineers, QA, and DevOps to deliver production-ready systems Continuously improve engineering practices, including leveraging AI to iterate faster You will be great for this role if you have: Strong programming experience in any modern language (e.g. Go, Java, Python, Kotlin, etc.). We care more about how you think and design systems than the specific language you use Solid understanding of system design, scalability, and distributed systems Experience building APIs and working with data storage systems Ability to learn new technologies quickly and pragmatically Strong problem-solving skills and a structured way of thinking Ownership mindset and collaborative approach to teamwork Interest in incorporating AI as part of your development workflow Nice to have: Experience with cloud platforms (e.g. AWS) Familiarity with containers and orchestration (Docker, Kubernetes) Experience with event-driven systems and messaging (e.g. Kafka) If you don’t meet every requirement but are excited about the role, we’d still love to hear from you. Why you should join SumUp Make an impact on a global scale - our systems serve millions of merchants Learn from experienced engineers while working on complex, real-world problems Be part of a tech-agnostic team that uses the right tools for the job Collaborate with SumUppers worldwide on large-scale fintech products used by millions, based in our Sofia office (office-first setup). Access a €2,000 annual L&D budget to attend conferences or advance your career through education. Enjoy 25 days of paid leave (increasing with tenure), plus paid vacations for special occasions and a 1-month sabbatical every 3 years. Benefit from extra perks like health and life insurance, co-sponsored Multisport cards, childbirth/adoption bonuses, discounts, a referral program, 100 EUR monthly food vouchers, 40 EUR flexible benefits, and more. About SumUp We believe in the everyday hero. Small business owners are at the heart of all we do, so we create powerful, easy-to-use financial solutions to help them run their businesses. With a founder’s mentality and a 'team-first’ attitude, our diverse teams across Europe, South America and the United States work together to ensure that the small business owners we partner with can be successful doing what they love. SumUp is an Equal Employment Opportunity employer that proudly pursues and hires a diverse workforce. SumUp does not make hiring or employment decisions on the basis of race, color, 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. SumUp also s