Senior Fullstack Engineer - Partnership & Enterprise

The Partnership and Enterprise squad is building the infrastructure that powers Sum Up's partner channel, a business that supports around 800 active partners and is growing fast. As the squad's Senior Full-Stack Engineer, you'll take end-to-end ownership of the Partner Portal, the product that sits at the heart of how Sum Up's partners manage their merchants, fees, and operations. This is an opportunity with real scope: you'll shape technical direction, collaborate closely with CRM engineers and product stakeholders, and ship features that directly reduce operational friction for the teams driving Sum Up's sales growth.

• Build and own the Partner Portal's frontend using React, Type Script, and Next.js, creating fast, reliable, and well-structured user-facing experiences
• Design, build, and maintain the services and microservices that power the portal, ensuring reliability and high availability at scale
• Write and maintain back-end APIs, services, and data pipelines in Type Script and Go that are scalable and built to support a fast-growing global platform
• Develop fee management functionality and other high-impact features that directly reduce the administrative burden on partner management teams
• Implement monitoring and alerting, and follow up on incidents to keep the platform stable and performant
• Collaborate with colleagues and stakeholders across the Partnerships team to identify areas of improvement, collect feature requests, and shape solutions
• Actively contribute to code reviews, team ceremonies, and chapter rituals, sharing context and knowledge across engineering disciplines to avoid silos

• You have proven experience with Type Script and React, building scalable, production-grade full stack applications using frameworks such as Next.js, Remix, Nuxt, or similar
• Solid experience designing and working with RESTful APIs and complex microservice systems, with comfort navigating and refactoring large codebases
• Solid knowledge of Go, or strong experience with another backend language such as Node.js, used to build reliable, performant backend services
• Experience as a Kubernetes user, with familiarity in CI/CD pipelines and infrastructure tooling such as Terraform
• Comfort working closely with CRM systems or adjacent tooling (e.g. Salesforce), and an openness to bridging the gap between CRM engineering and full stack development
• A product mindset, connecting technical decisions to real business outcomes, and a genuine sense of ownership over the features you build from planning through to maintenance

• 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
• Enrolment onto our Virtual Stock Option programme: you will own a stake in Sum Up's future success
• A dedicated annual L&D budget of €2000 for your individual development, which can be used to attend conferences and/or advance 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 Sum Up team

Be empowered to do more that matters.

At Sum Up, we're on a mission to empower small businesses across the globe by providing simple and affordable tools that allow them to thrive. Today, over 4 million businesses in 37 markets rely on Sum Up as their financial partner to manage payments, finance and customer relationships.

Our commitment to small businesses is reflected in our diverse team of over 3,000 Sum Uppers from over 90 nationalities, united by global collaboration and an innovative…