Senior Backend Engineer – Kotlin/Spring, Scale Online Payments

SumUp; Warszawa; Hybrid; PLN 210,000 - 331,000; Full time

Benefits offered by this job

Hybrid Warsaw office

Stock options

L&D budget €2000

Fitness on-site

Health + life insurance

26 paid days off

Sabbatical after 3 years

Referral bonus

Job summary

SumUp is hiring a backend engineer to join the Sell Online Tribe in Warsaw, focusing on the Bookings product. You will design, build, and maintain scalable backend services, collaborating with frontend and mobile teams to deliver robust APIs across web, iOS, and Android.

The role requires 5+ years in backend development, strong Kotlin/Java and Spring Boot, and hands-on experience with PostgreSQL, Kafka, Docker, Kubernetes, and AWS. Hybrid work in Warsaw with excellent growth opportunities.

Qualifications

• 5+ years of professional backend engineering experience.
• Fluent in Kotlin (or Java) with deep Spring Boot experience.
• Experience with PostgreSQL, Kafka, Docker, Kubernetes, and AWS.
• Understanding of RESTful APIs, distributed systems, and event-driven architectures.
• Experience with CI/CD pipelines, GitHub Actions, and observability tools.

Responsibilities

• Design, build, and maintain scalable backend systems supporting SumUp's Bookings product.
• Collaborate with frontend and mobile engineers to deliver new features and improve APIs across web, iOS, and Android.
• Participate in technical planning, code reviews, and design discussions to ensure clean, testable, and maintainable code.
• Continuously optimise performance, ensure observability, and uphold our high reliability standards.
• Actively contribute to shaping the technical roadmap for the Sell Online platform.

Skills

Backend engineering

Kotlin/Java

Spring Boot

RESTful APIs

CI/CD

Observability

GitHub Actions

Grafana/Honeycomb

Distributed systems

gRPC/Protobuf (nice)

PostgreSQL

Kafka

Docker

Kubernetes

AWS

Tools

PostgreSQL

Kafka

Docker

Kubernetes

AWS

Job description

SumUp is hiring a backend engineer to join the Sell Online Tribe in Warsaw, focusing on the Bookings product. You will design, build, and maintain scalable backend services, collaborating with frontend and mobile teams to deliver robust APIs across web, iOS, and Android.

The role requires 5+ years in backend development, strong Kotlin/Java and Spring Boot, and hands-on experience with PostgreSQL, Kafka, Docker, Kubernetes, and AWS. Hybrid work in Warsaw with excellent growth opportunities.