Senior Backend Engineer - Cards

About the role

SumUp is looking for a Senior Backend Engineer to join the Cards squad in Berlin. You will own and build high‑throughput, cloud‑native services that power card issuing, lifecycle management and transaction processing for merchants across Europe.

Key responsibilities

• Design, develop and operate end‑to‑end backend services for the Cards EU domain, including observability, testing and production support.
• Shape the technical roadmap by participating in architectural discussions and proposing solutions for distributed‑system challenges.
• Write well‑scoped pull requests, conduct thorough code reviews and maintain high standards of code quality and test coverage.
• Collaborate with adjacent engineering squads and product managers to refine the backlog and deliver features.
• Participate in incident reviews and on‑call rotation, ensuring reliability of the services you build.
• Apply AI tooling to accelerate engineering workflows and raise the team’s AI literacy.

Required profile

• Proven experience delivering production‑ready backend services end‑to‑end on a modern cloud‑native stack.
• Strong hands‑on background with Kotlin and interest in Java, Golang or Elixir.
• Deep understanding of distributed systems, API design, data modelling and relational databases.
• Practical experience with containerisation, orchestration and CI/CD pipelines.
• Ability to turn ambiguous product problems into clear technical solutions with minimal guidance.
• Excellent written and spoken English and a curiosity for the fintech product domain.

Required skills

• Kotlin
• Java
• Golang
• Elixir
• Distributed systems
• API design
• Relational databases
• Containerisation
• Orchestration
• CI/CD
• Cloud‑native architecture
• Monitoring and observability
• AI tooling

What we offer

• Work on large‑scale fintech products used by millions of businesses worldwide.
• Collaborate with a global team from a modern Berlin office.
• Opportunity to influence core card‑issuing and payment systems.