Backend Engineer

Sumup

SumUp’s Point-of-Sale (POS) solution empowers cafes, shops, bars, hair salons, and other businesses to operate efficiently and grow. It offers a wide range of features, including product catalogs, inventory management, business analytics, compliance support, and loyalty tools. As a Backend Engineer in the Orders & Sales or Catalog Platform team, you will build the engine powering core infrastructure for over 4 million businesses worldwide. Whether you are architecting global sales APIs or scaling item management systems, your work is central to the SumUp ecosystem. The Orders & Sales team builds high-performance APIs and receipt engines that unify transaction and sales data, utilizing an AI-native mindset and extreme collaboration. Meanwhile, the Catalog Platform team owns the backend for item management, variants, categories, and taxes, focusing on high-stakes reliability and core POS infrastructure scaling. WHAT YOU’LL DO * Develop and evolve high-performance backend services and APIs using Kotlin and Spring Boot. * Design and maintain robust data schemas and event-driven integrations (Kafka) to handle complex transaction and catalog data at scale. * Write clean, well-tested, production-grade code and contribute meaningfully to code reviews and team rituals. * Collaborate with mobile and product teams to ship end-to-end features with a focus on performance and data consistency. * Engage in daily pair programming to solve complex concurrency challenges and maintain high architectural standards. * Take full ownership of the development lifecycle, including managing CI/CD pipelines and monitoring service health in production. * Actively use and experiment with AI coding agents to automate repetitive tasks and increase shipping velocity. * Refactor and migrate mission-critical domain logic to centralize and simplify the "Sales" and "Catalog" experiences across the ecosystem. YOU’LL BE GREAT FOR THIS ROLE IF * You have 3+ years of experience in backend engineering with the JVM stack (preferably Kotlin and Spring Boot). * You have a solid understanding of software design patterns, data modeling, and fundamental system architecture principles. * You are comfortable working with Kafka, Postgres, and AWS in a production environment at scale. * You enjoy and actively seek out collaboration and daily pair programming as a primary way of working. * You are an "AI-native" engineer, open to using agents and tools to optimize your coding process. * You have experience with, or a strong interest in, distributed and fault-tolerant systems. * You are a fast learner who values quality, detail, and effective time management. * You are fluent in English and can communicate clearly with both technical and non-technical stakeholders. NICE TO HAVE * Experience with Kubernetes and cloud-native observability/monitoring tools. * Knowledge of different programming paradigms (Functional vs. OOP). * Familiarity with high-scale applications involving many concurrent processes. * A desire to share knowledge with the wider engineering community. Why you should join SumUp 🌎 Opportunity to work with SumUppers globally on large-scale fintech products used by millions of businesses worldwide, from our Berlin office. This involves an office-first setup 🌈 Commitment to Diversity and Inclusion: be part of a workplace that values and promotes diversity, fostering an inclusive environment where everyone's perspectives are respected and embraced 🚀 Enrolment onto our Virtual Stock Option programme: you will own a stake in SumUp’s future success 📚 A dedicated annual L&D budget of €2000 for your individual development, which you can be used to attend conferences and/or advancing your career through further education 💶 A corporate pension scheme where we match up to 20% of your contributions 🏖️ Generous time off: enjoy 28 days of paid leave plus public holidays and special leave days 🚵🏾‍♂️ Numerous other benefits such as Urban Sports Club subsidy, Kita placement assistance, subsidised office lunches 🌴 Break4me: 1-month sabbatical after 3 years of service 🔗 Referral Bonus: earn additional rewards by referring talented individuals to join the SumUp team About SumUp We believe in the everyday hero. Small business owners are at the heart of all we do, so we're creating tools that help them run their businesses. With a founder’s mentality and a 'team-first’ attitude, our diverse teams across Europe, South America and the United States work together to ensure that the small business owners we partner with can be successful doing what they love.  SumUp is an Equal Employment Opportunity employer that proudly pursues and hires a diverse workforce. SumUp does not make hiring or employment decisions on the basis of 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. SumUp also strives for a healthy and safe workplace and strictly prohibits harassment of any kind. SumUp will not accept unsolicited resumes from any source other than directly from a candidate. Job Application Tip We recognise that candidates feel they need to meet 100% of the job criteria in order to apply for a job. Please note that this is only a guide. If you don’t tick every box, it’s ok too because it means you have room to learn and develop your career at SumUp. Job Application Tip We recognise that candidates feel they need to meet 100% of the job criteria in order to apply for a job. Please note that this is only a guide. If you don’t tick every box, it’s ok too because it means you have room to learn and develop your career at SumUp.

Sumup

In the Global Bank tribe, we're building the infrastructure to provide merchants with a digital business account that empowers them to manage their banking needs. Our goal is to become the most popular banking partner for small merchants globally with an effortless, simple, and affordable experience. You'll help us transition from fragmented regional setups to a unified global infrastructure, directly enabling millions of merchants worldwide to access seamless banking tailored to their needs. As a Senior Backend Engineer on the Global Accounts team, you'll own critical pieces of our bank account platform. You'll help us design and build a fully distributed, event-driven system designed to scale across regions with resilience and compliance built in. You'll work primarily in Kotlin, with opportunities in Elixir and Golang. We practice Extreme Programming: small iterations, daily deliveries, and a focus on technical design quality and deep problem understanding. Our tech stack includes Kotlin, Golang, Elixir, Java, AWS, Kafka, PostgreSQL, and Kubernetes, supported by observability tools like Prometheus, Grafana, and Honeycomb. We also use AI-assisted development tools including Cursor and GitHub Copilot. What You'll Do * Build critical infrastructure from scratch: Contribute to the design and implementation of a newly architected global accounts platform. You'll help migrate existing systems to a modern, event-driven, decoupled architecture that enables scalability and resilience across regions. * Master event-driven architecture: You'll be working extensively with Kafka to build a truly decoupled, resilient system. Event-driven architecture is essential to our goal of ensuring that failures in one part of the system don't bring down banking operations globally. This isn't just a technical requirement—it's the foundation of building a platform that can handle the complexities of multi-region banking. * Solve complex compliance challenges: Design flexible systems that handle varying regulatory and verification requirements across different regions and use cases. You'll make compliance requirements maintainable and natural rather than an afterthought. * Enable other teams: Build a self-service platform that empowers internal teams across the organization to contribute to and build on top of. * Work globally: Your work will directly impact EU and LATAM markets, with potential US expansion on the horizon. You'll Be Great for This Role If * Strong technical foundation: Solid backend development experience in Kotlin, with interest in working across multiple languages (Golang, Elixir). You understand system architecture, object-oriented and functional design principles, data modeling, and API design (RESTful and event-driven). * Event-driven architecture expertise: Proven experience with Kafka and event-driven systems. You understand how this enables true decoupling and resilience in distributed systems. * Distributed systems mastery: You've built tested, observable, scalable, robust, and fault-tolerant distributed systems. You have hands-on experience with AWS, Docker, Kubernetes, cloud-native architectures, and relational databases, understanding data consistency and performance considerations. * Ownership and craft: You take full ownership of the software you ship, from design to production readiness. You value clean, maintainable code and continuously refactor to keep designs simple and scalable. * Motivated by the challenge: You're curious and energized by complex problem-solving rather than just shipping features quickly. You thrive in environments with fast iterations and careful design, where understanding the problem deeply is valued over rushing to delivery. You're excited by the opportunity to architect critical systems from scratch and work in a team that practices Extreme Programming with daily deliveries. * Collaborative mindset: You communicate respectfully, share knowledge openly, and actively support your teammates' growth. Why you’ll enjoy working at SumUp * Be 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. * Be part of a global tribe building a banking solution from the ground up and delivering impactful solutions to the real-life problems of millions of SumUp merchants all over the world * Career growth and learning opportunities: We invest in your development through regular training, mentorship programs, SumUp University leadership cohort and a yearly learning budget (2,000 EUR) * Sabbatical program for tenured SumUppers * Join a global team where you belong: Check out our D&I Initiatives and Employee Resource Groups such as Pride Club, SumAfro, Neurodiversity, Grupos Mais, Women in Tech, and more * Health & wellness benefits: in-house fitness classes, gym in the office, subsidized Urban Sports Club and available psychotherapy sessions * A lot of other benefits such as Subsidized Public Transport Card, Kita placement assistance, Pension Scheme, Language Learning platform/courses etc. * Enrollment onto our virtual stock ownership program - you will own a stake in SumUp’s future success     About SumUp At SumUp, we’re on a mission to empower small businesses around the world with simple, affordable tools to help them start, run, and grow. More than 4 million merchants across 37 markets trust us as their financial partner — and we’re just getting started. We’re a global team of 3,000+ people from over 90 nationalities, united by curiosity, collaboration, and care. Our core valuesOpens in new window and cultureOpens in new window shape everything we do, fostering inclusion, learning, and belonging. SumUp is proud to be an Equal Employment Opportunity employer, committed to building a safe, respectful, and diverse workplace where everyone can thrive. 👉 Explore more about our culture on our careers site, or follow us on LinkedInOpens in new window and InstagramOpens in new window. SumUp 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. Job Application Tip We recognise that candidates feel they need to meet 100% of the job criteria in order to apply for a job. Please note that this is only a guide. If you don’t tick every box, it’s ok too because it means you have room to learn and develop your career at SumUp.

Sumup

In the Global Bank tribe, we're building the infrastructure to provide merchants with a digital business account that empowers them to manage their banking needs. Our goal is to become the most popular banking partner for small merchants globally with an effortless, simple, and affordable experience. As part of the Bank Activation and Revenue team, you will join a high-impact growth engine within the bank. Our mission is to guide merchants in unlocking the most value out of their SumUp Business Account during their activation journey: we aim to convert 100% of SumUp’s ecosystem users into active Bank users. We own the critical journey from the moment a merchant opens an account until they understand how the business account can solve their business needs, making it part of their daily routine. To achieve this at scale, we are building a greenfield activation and engagement platform consisting of a series of initiatives and experiments to drive adoption and engagement of SumUp users with the business account. Your work will directly drive revenue by enabling seamless cross-selling of the entire SumUp product suite to millions of merchants. What You’ll Do * Build Greenfield Services: Design and implement the trifecta of services (Banners, Rewards, and Feature Toggles) from the ground up to power global product experimentation. * Drive Activation: Create the technical logic that tracks and incentivizes users through their first five meaningful transactions, ensuring a smooth path to becoming a long-term banking partner. * Own the Stack E2E: We follow a “build it, run it, own it” model. You will be responsible for the full lifecycle of your features, from architectural design to production monitoring. * High-Velocity Engineering: Participate in a culture of daily deliveries. We value moving fast, testing hypotheses, and iterating based on real-world data. * Bridge Client & Backend: Build robust APIs that power the mobile and web banking experience while managing complex asynchronous processing for rewards and incentives via Kafka. * Collaborate with Stakeholders: Work closely with other engineering teams across the Bank and the wider SumUp ecosystem to ensure our activation tools are easily integrable and highly scalable. You’ll be great for this role if * Strong technical foundation: Solid backend development experience in Golang, with interest in working across multiple languages (Kotlin, Elixir). You understand system architecture, object-oriented and functional design principles, data modeling, and API design (RESTful and event-driven). * Growth Mindset: You're curious and energized by complex problem-solving. You thrive in environments with fast iterations and careful design, where understanding the problem deeply is valued over rushing to delivery. You're excited by the opportunity to architect critical systems from scratch - like our new global banner service - and work in a team that follows a "build it, run it" model with daily deliveries. * Systems Pragmatist: You understand that supporting and evolving legacy systems is the foundation for future success. You take pride in making existing code better while ensuring new services are architected for the long haul. * Ownership and craft: You take full ownership of the software you ship, from design to production readiness. You value clean, maintainable code and continuously refactor to keep designs simple and scalable. * Communication: You can communicate complex technical trade-offs effectively to your fellow engineers and technical stakeholders. What You'll Achieve in 6 Months By your sixth month, you will have taken full ownership of one of our Rewards features and contribute to the Banners service. Banners service will be the primary engine for product discovery and cross-selling within the Bank app, enabling our team to run rapid-fire experiments that directly impact SumUp's bottom line. Any of the following would be considered a plus * Previous experience in a Growth-focused engineering team. * Experience building rules engines or Reward/Incentive systems. * Familiarity with the Fintech or Banking regulatory landscape. Why you’ll enjoy working at SumUp * Be 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. * Be part of a global tribe building a banking solution from the ground up and delivering impactful solutions to the real-life problems of millions of SumUp merchants all over the world * Career growth and learning opportunities: We invest in your development through regular training, mentorship programs, SumUp University leadership cohort and a yearly learning budget (2,000 EUR) * Sabbatical program for tenured SumUppers * Join a global team where you belong: Check out our D&I Initiatives and Employee Resource Groups such as Pride Club, SumAfro, Neurodiversity, Grupos Mais, Women in Tech, and more * Health & wellness benefits: in-house fitness classes, gym in the office, subsidized Urban Sports Club and available psychotherapy sessions * A lot of other benefits such as Subsidized Public Transport Card, Kita placement assistance, Pension Scheme, Language Learning platform/courses etc. * Enrollment onto our virtual stock ownership program - you will own a stake in SumUp’s future success About SumUp At SumUp, we’re on a mission to empower small businesses around the world with simple, affordable tools to help them start, run, and grow. More than 4 million merchants across 37 markets trust us as their financial partner — and we’re just getting started. We’re a global team of 3,000+ people from over 90 nationalities, united by curiosity, collaboration, and care. Our core valuesOpens in new window and cultureOpens in new window shape everything we do, fostering inclusion, learning, and belonging. SumUp is proud to be an Equal Employment Opportunity employer, committed to building a safe, respectful, and diverse workplace where everyone can thrive. 👉 Explore more about our culture on our careers site, or follow us on LinkedInOpens in new window and InstagramOpens in new window. SumUp 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. Job Application Tip We recognise that candidates feel they need to meet 100% of the job criteria in order to apply for a job. Please note that this is only a guide. If you don’t tick every box, it’s ok too because it means you have room to learn and develop your career at SumUp.