Senior Full-Stack Engineer

About the team

As part of the Acquisition Domain, you will work on building and scaling the systems that power how Sum Up acquires and onboards merchants across all channels. The team operates within the Acquisition Tribe, focusing on developing end‑to‑end platforms and tools used by Sales, Partner Acquisition, and Account Management teams on a daily basis.

You will contribute across the stack—designing and building backend services, APIs, and frontend applications that support acquisition workflows such as lead management, partner integrations, and onboarding processes. This includes developing user‑facing interfaces that enable internal teams to interact with complex systems efficiently, while ensuring a seamless and intuitive experience.

From a technical perspective, the team works with microservices architecture, event‑driven systems, and modern frontend frameworks, handling high volumes of operational data and enabling real‑time interactions across systems. You'll collaborate closely with Product, Data, and other engineering teams to define scalable system designs, clean interfaces, and strong data contracts, while continuously improving system reliability, performance, and developer experience across the stack.

• Design, build, and maintain end‑to‑end features across backend services and frontend applications that support merchant acquisition and onboarding workflows
• Develop and evolve scalable APIs and user‑facing tools used by Sales, Partner Acquisition, and Account Management teams
• Build intuitive frontend interfaces that simplify complex operational processes and improve internal user experience
• Ensure data consistency and reliability across systems that handle leads, partner integrations, and acquisition pipelines
• Write high‑quality, maintainable code across the stack, following Platform standards and engineering best practices
• Improve system performance, observability, and reliability, ensuring smooth operation of business‑critical tools
• Collaborate closely with Product, Data, and cross‑functional teams to translate business needs into scalable, user‑centric solutions

• 5+ years of professional experience, with strong proficiency in Type Script and React
• Hands‑on experience building full‑stack applications using modern frameworks such as Next.js, Remix, Nuxt, or similar
• Strong experience designing and consuming RESTful APIs within a microservices environment, ideally supporting data‑heavy or workflow‑driven systems
• Experience working with SQL and event‑driven architectures (e.g. Postgres, Kafka), especially in systems that handle operational data such as leads, onboarding flows, or partner integrations
• Good understanding of system architecture, software design principles, data modeling, and API design, with the ability to build scalable and maintainable systems
• Experience building internal tools or user‑facing applications that improve workflows and usability for non‑technical users (e.g. Sales or Operations teams)
• A collaborative mindset with strong communication skills, openness to feedback, and a clear sense of ownership over delivered features and systems

• Opportunity to work with Sum Uppers 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
• Dedicated annual L&D budget of €2,000 for attending conferences and/or advancing your career through further education
• Enrolment onto our VSOP program:
  You will own a stake in Sum Up's future success
• A corporate pension scheme where we match up to 20% of your contributions
• 30 Days Sabbatical:
  Enjoy the unique opportunity to take a well‑deserved break with our 30 days sabbatical benefit after completing 3 years of employment with Sum Up
• Referral Bonus:
  Earn additional rewards by referring talented individuals to join the Sum Up team
• Numerous other benefits such as Urban Sports Club subsidy, Kita placement…