ING Backend Engineer interview questions & guide 2026

Preparation for ING requires a solid grasp of both theoretical computer science and practical, real-world application. The following questions are representative of the patterns observed in past interviews; use them to gauge your readiness and identify areas for deeper study.

Core Java and Frameworks

These questions test your mastery of the language and the ecosystem most commonly used at ING.

• How do you manage memory in Java, and what are the common pitfalls with garbage collection?
• Explain the lifecycle of a Spring Bean and the different scopes available.

To succeed at ING, you must demonstrate that you can move beyond syntax and understand the "why" behind your technical choices. Preparation should focus on articulating your thought process clearly while maintaining a focus on clean, scalable code.

• Role-related knowledge: You must show deep proficiency in Java and the Spring ecosystem. Be prepared to discuss not just how to use these tools, but how they function under the hood.
• Problem-solving ability: Interviewers look for a structured approach to ambiguous problems. Break down requirements logically, state your assumptions, and validate your solution with edge cases.
• Communication and Collaboration: Whether it is pair programming or a behavioral discussion, your ability to articulate trade-offs is key. Explain why you chose a specific design pattern or data structure over the alternatives.
• Culture fit: ING values professional, team-oriented engineers. Be ready to discuss your past projects, how you handle feedback, and your experience working in agile environments.

The interview process at ING is designed to evaluate both your technical depth and your alignment with the team’s working style. Candidates typically go through an initial screening followed by one or more technical rounds, which may include a coding assessment or a live pair-programming session.

The pace of the process can vary by region and team, and it is common for the evaluation to be thorough. You should expect to engage with both technical leads and potentially peers, focusing on your ability to contribute to a collaborative development environment.

This visual timeline highlights the progression from initial screening to technical evaluation. You should use this to pace your study—prioritize coding practice for the early stages and architectural/behavioral preparation for the later, more senior-led interviews.

Technical Depth and Coding

Technical interviews at ING focus on your ability to write production-ready code. You will be evaluated on your mastery of core language concepts and your ability to optimize solutions.

Be ready to go over:

• Collections Framework: Understanding the time complexity of various operations.
• OOP Principles: Demonstrating how to use inheritance, polymorphism, and encapsulation to create modular code.
• Spring Boot Ecosystem: Knowledge of dependency injection, annotations, and configuration.

Example scenarios:

• Refactoring a provided code snippet to improve efficiency.
• Explaining the trade-offs between different data structures for a specific storage problem.

Architectural Thinking

As a Backend Engineer, you are expected to understand how services interact within a larger system.

Be ready to go over:

• RESTful API Design: Best practices for versioning, status codes, and security.
• Microservices: Understanding how to handle inter-service communication and eventual consistency.
• Testing: The importance of unit and integration testing in maintaining system reliability.

As a Backend Engineer, you will spend your time designing and implementing backend services that support our diverse product portfolio. You will participate in the full software development lifecycle, from gathering requirements and writing technical specifications to deploying and monitoring services in production.

Collaboration is central to your success. You will work closely with frontend engineers, product owners, and DevOps teams to ensure seamless integration. You will also participate in code reviews, contributing to the team's collective knowledge and maintaining high standards for code quality and security across the organization.

A strong candidate for this role possesses a blend of technical expertise and a proactive, problem-solving mindset. We look for individuals who are comfortable with the complexity of modern distributed systems.

• Must-have skills: Proficient in Java (version 8+), deep experience with Spring Boot, and familiarity with SQL/NoSQL databases.
• Nice-to-have skills: Experience with cloud platforms (e.g., Azure or AWS), containerization tools like Docker or Kubernetes, and familiarity with CI/CD pipelines.

Q: How difficult are the technical assessments? A: The technical assessments, such as those conducted via platforms like Codility, are designed to be challenging but fair. They test your ability to handle algorithmic problems and your knowledge of core language features.

Q: What should I do if I haven't heard back from the recruiter? A: If you have not received a response within the expected timeframe, it is professional to send a polite follow-up email. While some delays occur, we encourage you to stay patient and continue your preparation.

Q: What is the most important thing to emphasize during the interview? A: Emphasize your ability to write clean, maintainable code and your willingness to collaborate. Technical skills are the baseline, but the ability to work effectively within a team is what differentiates top candidates.

• Practice live coding: Do not just solve problems on paper; practice talking through your logic while you type.
• Know your CV: Be prepared to explain every project you have listed in detail, including the technologies used and the challenges you overcame.
• Focus on trade-offs: Whenever you suggest a solution, briefly mention why it is better than the alternative. This demonstrates senior-level thinking.
• Prepare questions for the interviewers: Ask about the team's current technical challenges or how they balance new feature development with technical debt.

The Backend Engineer role at ING offers an unparalleled opportunity to work on high-impact financial systems at scale. By focusing your preparation on mastering the Java/Spring ecosystem, refining your problem-solving process, and demonstrating a collaborative mindset, you will position yourself as a strong candidate.

Remember that interview processes are learning experiences. Even if you encounter challenges, use every interaction to refine your approach. For further insights and to track your progress, continue utilizing the resources available on Dataford. You have the potential to make a significant contribution to our team—prepare thoroughly and walk into your interviews with confidence.