Senior Backend Engineer (Kotlin/JVM)
SumUp's Transfers Excellence squad, within the Global Bank, owns the core services that move money for merchants and consumers, including IBAN-based transfers and peer-to-peer payments. The team is replacing market-specific implementations with a single, unified global transfer platform serving Europe, the UK, Brazil, Chile and eventually the US and Canada. The role is based in the Sofia office, and the stack includes Kotlin, Java, Go, Elixir, AWS, Kafka, PostgreSQL and Kubernetes.
Responsibilities
- ▹Build and maintain backend services at the heart of SumUp's transfer infrastructure, with end-to-end ownership from development through observability, testing and production support
- ▹Contribute to the migration from market-specific services toward a unified global transfer platform, working across active services and legacy systems being decomposed
- ▹Raise well-scoped pull requests, conduct thorough code reviews and maintain high standards of code quality and test coverage
- ▹Participate in incident reviews and the on-call rotation, taking accountability for service reliability
- ▹Contribute to the technical roadmap through architectural discussions and solutions for complex distributed systems challenges
- ▹Apply AI tooling to accelerate engineering workflows and raise the team's AI literacy
Requirements
- ▹Solid experience as a backend software engineer in modern languages such as Kotlin, Go or Java (Kotlin is the team's primary language)
- ▹Solid understanding of distributed systems and event-driven architecture
- ▹Experience with async processing and messaging tools like Kafka or similar
- ▹Experience with microservice architectures including Spring Boot and event-driven patterns, plus solid knowledge of relational databases and API design
- ▹Comfort working in high-throughput, regulated environments where reliability matters, with defensive coding and attention to edge cases
- ▹Clear communication in written and spoken English and a collaborative approach across global teams
- ▹Curiosity about product impact, not just the code
Soft skills
What we offer
- ▹Virtual Stock Option programme
- ▹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), plus public holidays and special leave
- ▹Additional health insurance and life insurance
- ▹On-site yoga and a co-sponsored Multisport card
- ▹Tax-free food voucher program plus Re:Benefits platform flexibility
- ▹Free shuttle buses to Joliot-Curie metro station
- ▹1-month sabbatical after 3 years of service (Break4me)
- ▹Referral bonus
About the company
SumUp builds simple, affordable financial tools for over 4 million small businesses across 37 markets, offering payments, business banking, lending, invoicing and money transfers. It is a global fintech with over 3,000 people across 20+ offices, with Sofia as one of its key engineering hubs, and is an Equal Employment Opportunity employer.