backend engineer for card payments

SumUp provides simple, affordable financial tools that help small businesses get paid, manage their money, and grow. Its products include payments, business banking, card products, lending, and invoicing. The Cards squad builds and operates systems for card issuing, lifecycle management, and transaction processing for merchants across Europe.

• Own and lead end-to-end delivery of backend services in the Cards EU domain, including observability, testing, and production support
• Contribute to the technical roadmap through architectural discussions and proposals for complex distributed systems challenges
• Create well-scoped pull requests, conduct code reviews, and maintain high standards of code quality and test coverage
• Collaborate with engineers in adjacent squads and the product manager to shape and refine the squad backlog
• Participate in incident reviews and the on-call rotation, taking accountability for service reliability
• Apply and champion AI tooling to accelerate engineering workflows and improve the team’s AI literacy

• Hands-on experience delivering production-ready backend services end-to-end, including testing, monitoring, and maintenance, on a modern cloud-native stack
• Production experience with Kotlin and openness to working with additional languages such as Elixir, Java, or Golang
• Solid understanding of distributed systems, API design, data modelling, and relational databases
• Hands-on experience with containerisation, orchestration, and CI/CD practices
• Ability to define a technical approach to an ambiguous product problem and lead it through implementation with minimal guidance
• Clear written and spoken English communication in a professional setting
• Curiosity about the product domain and ability to consider user experience during feature refinement
• Будет плюсом: None

• The role is office-first in the modern Sofia office
• Virtual Stock Option programme
• Annual L&D budget of €2000 and 10 paid days of educational leave
• 25 Days of paid leave, plus one extra day per year of service up to 35, public holidays, and special leave options
• Additional health insurance and life insurance
• On-site yoga and a co-sponsored Multisport card
• Tax-free food voucher programme and flexibility via the Re:Benefits platform
• Free shuttle buses to Joliot-Curie metro station
• One-month sabbatical after 3 years of service
• Referral bonus