(Senior) Backend Engineer - Balance Management

• What You’ll Do
• Build and evolve Sum Up’s core banking services that powers ledger operations and transactions, transforming regional systems into a unified, scalable global platform.
• Tackle complex distributed systems challenges, ensuring resilient services that continue to perform under high transaction volumes.
• Support modernization initiatives by improving observability, adding test coverage, refactoring code for long-term maintainability, and gradually introducing new architectural patterns without disrupting live banking operations.
• Contribute to key architectural decisions – build ledger and transaction history systems from the ground up, ensuring a globally scalable banking solution for our clients.
• Collaborate with teams across Risk, Treasury, Finance, and Infrastructure to ensure smooth, compliant, and reliable global operations.
• Take ownership from design to production, running the services you build, monitoring their performance, and continuously improving how we deliver high-quality software at scale.

Qualifications

• Solid backend experience building reliable, high-volume services and a careful approach to system design, APIs, data modeling, and service interactions.
• Proficiency in Golang and comfort learning and working with other languages as needed, e. g. Kotlin or Elixir.
• Write maintainable, well-tested code, follow CI/CD best practices, and take responsibility for the software you build from development to production.
• Comfortable building, deploying, and running services in cloud environments like AWS using Docker and Kubernetes.
• Eagerness to learn about relational databases that perform well under load and maintain data consistency.
• Collaborator who enjoys working across regions, communicating clearly, exchanging feedback effectively, and making thoughtful technical decisions together.
• Curiosity for building reliable financial services and the banking domain.
• Nice to Have
• Knowledge of Elixir – helpful given some of our legacy services are written in Elixir.
• Deeper Postgre SQL experience – performance tuning, complex queries, or schema design.
• Experience with event streaming platforms (Kafka preferred) and modern observability stacks (Grafana, Honeycomb, etc.).

Benefits

• Part of a company that values diversity and celebrates unique perspectives.
• Work with a global team of skilled professionals in an environment that fosters collaboration, learning, and growth.
• Opportunity to work on large‑scale fintech products used by millions of businesses worldwide.
• 25 days’ paid leave, plus 1 additional day for each year of employment.
• Up to 10 days of educational leave to expand your skill set.
• Career growth and learning opportunities: regular training, mentorship programs, Sum Up University leadership cohort, and a yearly learning budget (2,000 EUR).
• Participation in a virtual stock ownership program – you will own a stake in Sum Up’s future success.
• Access to the Sum Up Sabbatical, our Employee Assistance Program for mental health.
• Join a global team where you belong: D&I Initiatives and Employee Resource Groups such as Pride Club, Sum Afro, Neurodiversity, Grupos Mais, Women in Tech, and more.
• Additional health insurance, a subsidized Multisport card, free shuttle buses from Joliot-Curie metro station, and other great benefits.
• Attend global offsites and/or hackathons.

Sum Up is proud to be an Equal Employment Opportunity employer, actively seeking and embracing diversity in our workforce.

We don’t make hiring or employment decisions based on race, colour, 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.

Our commitment extends beyond recruitment to creating a safe and respectful workplace where harassment of any form is strictly prohibited.

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