Senior Backend Engineer - Identity Lifecycle

About the team

You’ll join one of the teams within Sum Up’s Identity Lifecycle Mission, working on some of the most critical building blocks behind the merchant journey, from onboarding and identity verification to KYC/KYB, regulatory data collection, and managing customer identity throughout the entire lifecycle.

Today, many of these capabilities live across different flows, legacy services, and tightly coupled integrations.

We’re on a journey to bring these pieces together into a more coherent, scalable platform, with shared data models, reusable services, and clear ownership boundaries.

As a Senior Backend Engineer, you won’t just be maintaining existing systems.

You’ll have the opportunity to shape how our identity platform evolves, modernise critical services, and help build foundations that can support new regulations, markets, and product requirements without reinventing the wheel every time.

You’ll be part of one dedicated team, but the challenges we tackle often cross team and domain boundaries.

You’ll work closely with Engineers, Product, Design, Compliance, Risk, and Operations, giving you the opportunity to influence solutions well beyond your own team.

If you enjoy solving complex backend problems, working in a highly collaborative environment, improving reliability, and building scalable capabilities that enable other teams to move faster, this could be an exciting opportunity to make a real impact at Sum Up.

What you’ll do

• Design, build, and operate scalable backend services, APIs, event-driven workflows, and system integrations.
• Build reusable capabilities that power merchant onboarding, identity verification, and KYC/KYB regulatory data collection.
• Drive reliability and resilience across critical services through better observability, failure handling, incident response, and long-term risk reduction.
• Work primarily with Go, while maintaining and progressively modernising existing services written in Java.
• Evolve domain models and service boundaries while reducing legacy complexity, duplicated logic, and tightly coupled integrations, always with a pragmatic, incremental mindset.
• Own your work end-to-end, from technical design and implementation to rollout and production follow-up.
• Work across team and domain boundaries, turning ambiguous product and regulatory requirements into clear, scalable technical solutions.
• Review code and designs, mentor engineers, and help raise engineering standards across the mission.

You’ll be great for this role if you have

• Strong professional experience building and operating production backend systems with high business impact.
• Experience working with Go and Java and confidence in maintaining and evolving existing Java services.
• Strong knowledge of API design, distributed systems, asynchronous processing, data modelling, testing, and system design.
• Experience with event streaming platforms such as Kafka and modern observability tools such as Grafana or Honeycomb.
• Experience deploying and operating services in cloud environments such as AWS, ideally with Docker and Kubernetes.
• A strong ownership mindset, with the ability to take complex problems from definition through to production.
• Experience improving the reliability of business-critical systems and turning recurring incidents into lasting engineering improvements.
• Strong communication skills and a collaborative approach to working across Engineering, Product, Compliance, Risk, and Operations.

Nice to have

• Experience in fintech, payments, KYC/KYB, identity verification, or regulatory systems.
• Experience translating regulatory and compliance requirements into clear, scalable engineering solutions, while helping bridge the gap between Compliance and Engineering.
• Why you should join Sum

Up

• 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
• We take learning and experimentation seriously with Hack Days every second Friday, and entire global Hack Weeks.
• 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

• A 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 assistance, relocation assistance,