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Senior Backend Engineer (Java) – Online Payments Platform

Sofia, Bulgaria · Engineering

SumUp is a preferred provider for card payments solutions for millions of small and medium businesses across the world. We’re now expanding our offering by developing a brand-new next gen online payments platform. 

To achieve this, we’re actively looking for software generalists with experience in online payments, who focus on solving problems, and see technology merely as a tool for it. 

Although we are long past the start-up phase, we continue to work in fully autonomous teams, each driving their part of the product end-to-end. 

On the tech side, we work on a number of different projects that span technologies, systems, and processes. A few of the technologies we're leveraging at SumUp include Java, Kotlin, Elixir, Ruby, Docker, Kubernetes, Redis, PostgreSQL.


  • Lay the foundations of our next generation payment platform

  • Develop modern scalable and highly available web and back-end applications

  • Participate in API design and implementation for both internal and external APIs

  • Own and maintain the business domain that your application touches

  • Implement clean, maintainable and testable code


  • You have vast experience with online payments/transaction processing systems that have high availability/throughput as a back-end engineer.

  • You have 5+ years’ relevant experience in agile large scale ecosystems and first-hand experience in mentoring.

  • You have a solid understanding of design principles and designing clear and predictable REST APIs.

  • You have practical experience with relational databases or data-modelling

  • You have a DevOps mindset and interest in AWS, Docker, Kubernetes, and/or Jenkins and a quality-first approach.

  • You are familiar with engineering best practices to write clean quality code

  • You have vast experience with micro-services architecture, Restful APIs and operating in a cloud environment, especially AWS.

  • You are open to learning different tools, frameworks, and languages to get the job done.

If you don’t meet the requirements 100%, we’d still love to hear from you. 


  • You’ll have the opportunity to build the foundations of our next generation payment platform.

  • You'll have the opportunity to make an impact as we work in flat hierarchies and with high autonomy.

  • You'll have the space to drive your career here and take ownership of projects.

  • You’ll be part of a diverse and international team.

  • You'll attend global offsites/hackathons/team events.

  • You'll receive competitive compensation and have access to an education budget.

  • You’ll receive 25 days paid vacation + 1 accumulative day for each year of employment at SumUp.

  • We offer additional health insurance, a subsidized Multisport card, free shuttle buses from Joliot-Curie metro station and other great benefits.

  • Innovative office design featuring an amazing 360 Sofia view, a music room, events forum space, fully equipped kitchen facilities; office relaxation activities such as yoga and massages.

You are welcome to have a look at developer documentation for online payments integrations:

About SumUp

We believe in the everyday hero. Those who have the courage to follow their passion and who have the strength and determination to realise their dreams.

Small business owners are at the heart of all we do, so we're creating powerful, easy-to-use financial solutions to 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 small business owners 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.