Internship Backend Engineer

Are you passionate about software engineering and eager to create solutions that make a real-world impact? Whether you’re a student, recent graduate, or looking to kickstart your career in tech, this is your chance to help small businesses succeed through SumUp’s innovative products and services, while gaining hands-on experience, mentorship, and career-launching opportunity.

SumUp is a global fintech company empowering over 4 million small businesses with tools for payments, banking, online stores, and more.

Our Bank Tribe builds the core infrastructure behind SumUp’s digital bank, used by merchants across Europe and Latin America. Within this team, the Cards team develops our card products, managing virtual and physical cards, and integrating with platforms like Google Pay and Mastercard.

As an intern on this team, you’ll have the opportunity to contribute directly to these projects, working on scalable solutions, tackling technical challenges, and gaining hands-on experience while seeing your impact firsthand.

What You’ll Learn & Do

• With the support of experienced mentors and teammates, you’ll:
• Learn to write clean, maintainable, and testable code in Kotlin and other backend languages
• Help build scalable systems and services powering card payments experiences
• Dive into distributed system design and event-driven architecture
• Learn best practices in DevOps, security, and site reliability
• Participate in code reviews, pair programming, and agile ceremonies
• Ship production-ready features and see your work go live
• Grow your skills in a supportive environment, with the goal of transitioning into a full-time software engineering role after the internship

You’ll be a great fit if you:

• Are a student, recent grad, or early-career developer excited about backend development
• Have academic, personal, or early professional experience in backend programming (either Kotlin, Golang or Java.)
• Are familiar with SQL and/or NoSQL databases like PostgreSQL, CockroachDB, or Kafka
• Have first experience in building or consuming RESTful APIs
• Eagerness to gain foundational understanding of system architecture, software design principles, and data modeling.
• Motivated to solve software engineering problems that deliver business value.
• Thrive in collaborative teams and enjoy learning through feedback
• Full-time availability 40h week, (min. 6 hrs/day or 30 hrs/week) is required for this role. Office-first setup in Sofia.

Why Join Us

• Grow your skills in a supportive environment, with the goal of transitioning into a full-time software engineering role after the internship
• Be part of a truly global team: 3000+ people, 80+ nationalities, 4 continents while also having a team right next to you in Sofia.
• Get hands-on experience on high-impact, high-scale systems that impact over 4 million users.
• Receive mentorship and guidance from experienced engineers, with the goal of transitioning you into a full-time role upon successful completion of the internship.
• Enjoy various benefits such as 25 days paid vacation, additional health insurance, Multisport card, monthly vouchers – for food and other benefits, and more.

Application Tips

We know that imposter syndrome is real. Even if you don’t meet every requirement, apply anyway. We’re looking for people who are excited to learn and grow.

🔗 Apply with your CV/LinkedIn and share your GitHub repo or project portfolio to show us what you’re passionate about.

More about us

We believe in the everyday hero.

Small business owners are at the heart of all we do, so we create 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 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, color, 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.