Senior Frontend Engineer - Sell Online

About Sumup

Be empowered to do more that matters.

At SumUp, we're on a mission to empower small businesses across the globe by providing a vast set of simple and affordable business tools to help them start, run, and grow their businesses. Today, over 4 million businesses in 36 markets rely on SumUp as their financial partner to manage payments, finance and customer relationships.

About The Team

You’ll join the Sell Online Tribe, the group shaping how merchants bring their businesses to life online. We design and build tools that help millions of entrepreneurs, from barbers to bakers, sell their products and services anywhere. Our focus is on Online Store and Bookings, two products at the heart of SumUp’s ecosystem. Together, they give merchants the power to manage appointments, showcase their offerings, and get paid—all from their phones.

We’re a cross-functional team of Product Managers, Designers, and Engineers who move fast, collaborate openly, and care deeply about crafting beautiful, performant mobile experiences. As part of this team, you’ll help us expand into new verticals, close the gap between web and mobile, and make digital selling effortless for small businesses everywhere.

What You’Ll Do

• Build and maintain modern, scalable web interfaces for the SumUp Bookings product using React and Next.js
• Collaborate with backend, design, and product teams to bring new features to life from concept to delivery
• Ensure a high-quality experience by writing testable, maintainable code and promoting best practices in code reviews
• Contribute to our design system and ensure a consistent, accessible user experience across devices
• Continuously optimise performance and improve observability and internationalisation in production environments

You’Ll Be Great For This Role If

• You have 4+ years of frontend development experience working with JavaScript and TypeScript
• You’re experienced with React.js, Next.js, and modern state management (e.g. Zustand, Context API)
• You have hands-on experience with Jest, React Testing Library, and solid understanding of CI/CD pipelinesYou’re skilled in building accessible and performant user interfaces, using tools like Tailwind or shadcn
• You understand REST APIs, internationalisation, and frontend observability (logging, performance metrics)
• You thrive in cross-functional teams, care deeply about user experience, and want to create products merchants love(Nice to have) Experience with Vercel, template engines, or working in SaaS/product-led tech companies

Why You Should Join Sumup (Warsaw) 🇵🇱

• 🌎 Opportunity to work , from our vibrant Warsaw office with inspiring art-filled lounges and a skyline terrace in the Mennica Legacy Tower. 
• 🌈 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 VSOP program: you will own a stake in SumUp’s future success 
• 🚴 Fitness support: work out on-site at our gym or explore the city using the Multisport Card, subsidised by SumUp for access to sports facilities across Warsaw 
• 🩺 Commitment to well-being: access health insurance coverage for you and your family, plus life insurance to further protect your peace of mind 
• 💰 PPK (Employee Capital Plan): grow your savings with joint contributions from SumUp and the State. 
• 🏖️ Generous time off: enjoy 26 days of paid leave plus public holidays and special leave days 🌴 Break4me: 1-month sabbatical after 3 years of service 
• 🔗 Referral Bonus: earn additional rewards by referring talented individuals to join the SumUp team

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.