Senior Backend Engineer – Golang

• Sum Up
• Publiée le11/04/2026
• Lieu Berlin, Germany
• Contrat On-site

In the Global Bank tribe, we’re building the infrastructure to provide merchants with a digital business account that empowers them to manage their banking needs.

Our goal is to become the most popular banking partner for small merchants globally with an effortless, simple, and affordable experience.

As part of the Bank Activation and Revenue team, you will join a high-impact growth engine within the bank.

Our mission is to guide merchants in unlocking the most value out of their Sum Up Business Account during their activation journey: we aim to convert 100% of Sum Up’s ecosystem users into active Bank users.

We own the critical journey from the moment a merchant opens an account until they understand how the business account can solve their business needs, making it part of their daily routine.

To achieve this at scale, we are building a greenfield activation and engagement platform consisting of a series of initiatives and experiments to drive adoption and engagement of Sum Up users with the business account.

Your work will directly drive revenue by enabling seamless cross‑selling of the entire Sum Up product suite to millions of merchants.

• What You’ll Do
• Build Greenfield Services: Design and implement the trifecta of services (Banners, Rewards, and Feature Toggles) from the ground up to power global product experimentation.
• Drive

Activation: Create the technical logic that tracks and incentivizes users through their first five meaningful transactions, ensuring a smooth path to becoming a long‑term banking partner.

• Own the Stack E2E: We follow a « build it, run it, own it » model.

You will be responsible for the full lifecycle of your features, from architectural design to production monitoring.

• High‑Velocity Engineering: Participate in a culture of daily deliveries. We value moving fast, testing hypotheses, and iterating based on real‑world data.
• Bridge Client & Backend: Build robust APIs that power the mobile and web banking experience while managing complex asynchronous processing for rewards and incentives via Kafka.
• Collaborate with

Stakeholders: Work closely with other engineering teams across the Bank and the wider Sum Up ecosystem to ensure our activation tools are easily integrable and highly scalable.

• You’ll be great for this role if
• Strong technical foundation: Solid backend development experience in Golang, with interest in working across multiple languages (Kotlin, Elixir).

You understand system architecture, object‑oriented and functional design principles, data modeling, and API design (RESTful and event‑driven).

• Growth

Mindset: You’re curious and energized by complex problem‑solving.

You thrive in environments with fast iterations and careful design, where understanding the problem deeply is valued over rushing to delivery.

You’re excited by the opportunity to architect critical systems from scratch – like our new global banner service – and work in a team that follows a « build it, run it » model with daily deliveries.

• Systems

Pragmatist: You understand that supporting and evolving legacy systems is the foundation for future success.

You take pride in making existing code better while ensuring new services are architected for the long haul.

• Ownership and craft: You take full ownership of the software you ship, from design to production readiness.

You value clean, maintainable code and continuously refactor to keep designs simple and scalable.

• Communication: You can communicate complex technical trade‑offs effectively to your fellow engineers and technical stakeholders.
• What You’ll Achieve in 6 Months

By your sixth month, you will have taken full ownership of one of our Rewards features and contribute to the Banners service.

Banners service will be the primary engine for product discovery and cross‑selling within the Bank app, enabling our team to run rapid‑fire experiments that directly impact Sum Up’s bottom line.

• Any of the following would be considered a plus
• Previous experience in a Growth‑focused engineering team.
• Experience building rules engines or Reward/Incentive systems.
• Familiarity with the Fin Tech or Banking regulatory landscape.
• Why you’ll enjoy working at Sum Up
• Be part of a company that values diversity and celebrates unique perspectives.
• Work with a global team of skilled professionals in an environment that fosters collaboration, learning, and growth.
• Be part of a global tribe building a banking solution from the ground up and delivering impactful solutions to the real‑life problems of millions of Sum Up merchants all over the world
• Career growth and learning opportunities: We invest in your development through regular training, mentorship programs, Sum Up University leadership cohort and a yearly learning budget (2,000 EUR)
• Sabbatical program for tenured Sum Uppers
• Join a global team where you belong: Check out our D&I Initiatives and Employee Resource Groups such as Pride Club, Sum Afro, Neurodiversity, Grupos Mais, Women in Tech, and more
• Health & wellness benefits: in-house f…
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