Senior Backend Engineer - Cards
SumUp's Cards squad owns the systems that power card issuing, lifecycle management and transaction processing for merchants across Europe, handling millions of card transactions every day. The team is scaling these systems for new product capabilities while laying the foundations for a more global, resilient platform. This seasoned backend engineer role is based in the Sofia office with an office-first setup and involves taking real ownership of complex, high-throughput distributed work.
Responsibilities
- ▹Own and lead the end-to-end delivery of backend services within the Cards EU domain, including observability, testing and production support
- ▹Contribute to the technical roadmap by participating in architectural discussions and proposing solutions for complex distributed systems challenges
- ▹Raise well-scoped pull requests, conduct thorough code reviews and help maintain high standards of code quality and test coverage
- ▹Collaborate closely with engineers in adjacent squads and with the product manager to shape and refine the 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 help raise the team's AI literacy
Requirements
- ▹Solid, hands-on experience delivering production-ready backend services end-to-end on a modern cloud-native stack, including testing, monitoring and maintenance
- ▹Production experience with Kotlin and openness to work 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 take an ambiguous product problem, define the technical approach and lead it to implementation with minimal guidance
- ▹Comfort working across teams and communicating clearly in written and spoken English
- ▹Genuine curiosity about the product domain
Soft skills
What we offer
- ▹Work on large-scale fintech products used by millions of businesses worldwide, from the modern Sofia office (office-first setup)
- ▹Virtual Stock Option programme - a stake in SumUp's success
- ▹Dedicated annual L&D budget of 2,000 EUR 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 program and the Re:Benefits platform
- ▹Free shuttle buses to Joliot-Curie metro station
- ▹Break4me: 1-month sabbatical after 3 years of service
- ▹Referral bonus
About the company
At SumUp, over 4 million businesses in 37 markets rely on the company as their financial partner to manage payments, finance and customer relationships. Beyond payments it offers business banking, card products, lending and invoicing. It is a diverse team of over 3,000 people from over 90 nationalities.