SumUp Data Engineer interview questions & guide 2026

The following questions are representative of the patterns observed in recent SumUp interview cycles. While the specific technical focus may shift depending on whether you are interviewing for a platform-focused or database-heavy role, these categories reflect the core competencies the team evaluates.

Technical Implementation & Coding

These questions assess your ability to write clean, functional, and production-ready code, specifically within the languages and paradigms favored by SumUp.

• Design an ETL solution using Go that uploads CSV files from a directory to a Postgres database.
• How do you ensure your data ingestion processes are idempotent, especially when handling file-based triggers?

Preparation for SumUp should focus on your ability to explain the "why" behind your technical choices. You are expected to demonstrate deep knowledge of your craft while maintaining a focus on the business impact of your engineering decisions.

Technical Proficiency – You must be prepared to write code that is not just correct, but robust and environment-agnostic. Interviewers will look for your ability to handle edge cases, such as infrastructure failures or unexpected data formats, with grace.

Architectural Thinking – You will be evaluated on your ability to design systems that scale. This means considering latency, data integrity, and the operational overhead of the solutions you propose.

Communication & Clarity – Whether you are in a technical coding session or a whiteboarding discussion, your ability to articulate your thought process is critical. Be prepared to explain your rationale, justify your trade-offs, and pivot if an interviewer challenges your initial assumptions.

The interview process at SumUp is structured to be direct and highly technical. Typically, the process begins with a screening call with the People team to align on your background and the role’s requirements. Following this, you can expect a rigorous technical phase, which may include a take-home assignment—often requiring proficiency in Go—or an in-person technical discussion where you are expected to whiteboard architectural solutions.

The final stages are designed to involve senior stakeholders, such as the CTO or engineering leads, to assess your potential for long-term impact within the team. The pace can be rapid, and you should be prepared for spontaneous scheduling and high expectations regarding your technical output.

This visual timeline illustrates the typical progression from initial screening to final technical evaluation. Use this to structure your preparation, ensuring you have refreshed your knowledge of both core programming fundamentals and high-level system design before your technical rounds.

Technical Rigor and Infrastructure

At SumUp, technical tasks are not just about passing tests; they are about building systems that function reliably in a production environment. You are evaluated on your ability to produce code that is clean, maintainable, and idempotent.

Be ready to go over:

• Idempotency – Ensuring that re-running a process does not duplicate data or create side effects.
• Environment Management – Best practices for ensuring your code runs consistently across development, staging, and production environments.

As a Data Engineer at SumUp, your day-to-day work centers on the reliability and performance of the data platform. You will spend a significant portion of your time coding robust ingestion services, optimizing database performance for high-throughput environments, and collaborating with product teams to understand data requirements.

You will frequently interface with other engineers to ensure that the data being produced by microservices is effectively captured and transformed. Projects often involve improving the observability of existing pipelines and migrating legacy systems to more modern, scalable architectures. The work is highly autonomous, and you are expected to take ownership of your solutions from the initial design phase through to deployment and maintenance.

A strong candidate for this role possesses a blend of deep technical skill and a pragmatic, problem-solving mindset. You should be comfortable working in a fast-paced environment where you are expected to deliver high-quality, production-ready code.

• Must-have skills – Proficiency in Go or similar systems-level languages, deep understanding of Postgres or other relational databases, and experience designing ETL/ELT pipelines.
• Nice-to-have skills – Experience with containerization (e.g., Docker, Kubernetes), cloud infrastructure (e.g., AWS, GCP), and familiarity with distributed data processing frameworks.
• Soft skills – Strong communication skills are essential for translating technical constraints into business outcomes and for working effectively within cross-functional teams.

Q: How difficult are the interviews at SumUp? A: Interviews are considered rigorous and technically demanding. They focus heavily on your ability to build real-world solutions rather than theoretical knowledge.

Q: What is the best way to prepare for the technical assignment? A: Focus on writing clean, production-ready code that handles errors and is easy to set up. Ensure your solution is idempotent and well-documented.

Q: What is the typical team culture like? A: The culture is fast-paced, direct, and outcome-oriented. Teams value ownership and the ability to work independently to solve complex engineering challenges.

Q: How long does the process usually take? A: The process is generally quick, though you should expect a high degree of intensity during the assessment phase.

• Own your narrative: Be prepared to talk in detail about the systems you have built in the past and the specific technical challenges you overcame.
• Clarify the format: If you are invited for an in-person or remote interview, do not hesitate to ask if it will be a "whiteboard" style session or a more casual discussion.
• Focus on observability: Always mention how you plan to monitor and maintain the systems you design.
• Be ready for feedback: The team values engineers who can handle constructive criticism of their design decisions during the interview.

The Data Engineer role at SumUp is a high-impact position that sits at the heart of the company’s fintech operations. By focusing your preparation on robust coding practices, architectural trade-offs, and clear communication, you will be well-positioned to succeed in the interview process. Remember that the team values engineers who can build reliable, scalable solutions while navigating the complexities of a fast-growing business.

You can explore additional interview insights, practice questions, and preparation resources on Dataford to further refine your strategy. With a structured approach and a focus on demonstrating your engineering maturity, you have the potential to make a significant contribution to the SumUp platform.

The compensation data provided reflects the market range for Data Engineer roles in the Berlin region. Candidates should use this as a baseline for understanding the total reward package, which typically includes a base salary and potential performance-based components, depending on the seniority level of the role.