Ing Deutschland Software Engineer interview questions & guide 2026

To help you prepare effectively, we have compiled representative questions based on real interview experiences at Ing Deutschland. These questions reflect the typical technical challenges, architectural discussions, and behavioral scenarios you are likely to encounter.

Backend & API Design

This category evaluates your ability to design clean, functional, and maintainable RESTful APIs, handle complex business logic, and write production-grade backend code.

• Design a set of REST APIs that calculate loan repayments based on principal, interest rate, and term.
• How do you handle validation and error states in a RESTful service to ensure a seamless client experience?

Preparing for an interview at Ing Deutschland requires a balanced approach that showcases your coding skills, architectural depth, and understanding of security principles. You should approach the process with a mindset focused on high-quality engineering and clear communication.

Technical Craftsmanship – You must demonstrate a commitment to writing clean, maintainable, and well-tested code. This is especially true during the take-home coding challenge, where reviewers look for solid design patterns, proper separation of concerns, and comprehensive test coverage.

Security-First Mindset – Working in fintech means security cannot be an afterthought. Be prepared to discuss security implications for almost every technical decision you make, from API design to database access.

Problem-Solving & Domain Knowledge – While prior banking experience is not always mandatory, you should be comfortable with financial concepts like loan calculations, interest rates, and transactional consistency. Show that you can translate complex business requirements into clear, logical code.

Resilience & Communication – The interview process can be rigorous, and technical reviews can be demanding. Demonstrating that you can communicate your ideas clearly, defend your technical choices rationally, and accept feedback gracefully is crucial.

The hiring process for a Software Engineer at Ing Deutschland is designed to evaluate both your practical coding abilities and your high-level architectural and security knowledge. Candidates can expect a multi-stage process that transitions from initial screening to hands-on implementation, culminating in deep-dive technical discussions.

The journey begins with an initial recruiter screening to assess mutual fit, followed by an offline technical assignment. This assignment is a critical gatekeeper in the process; it typically involves building a functional microservice or set of APIs. Once submitted, your code undergoes a rigorous review by company engineers. If your submission meets their standards, you will move forward to technical interviews where you will present your solution, discuss architectural choices, and face deep-dive questions on security and system design.

The timeline above outlines the standard progression of stages from your first contact to the final decision. Candidates should use this roadmap to pace their preparation, ensuring they allocate sufficient time to polish their coding challenge before submission. Be aware that response times between stages can sometimes vary, so maintaining proactive communication with your recruiter is highly recommended.

To stand out in the Ing Deutschland hiring process, you must excel in three core technical evaluation areas. Understanding what interviewers look for in each area will allow you to tailor your preparation effectively.

Clean Code & API Design

This area evaluates your ability to translate a business problem into a working, elegant software solution. During the take-home challenge, you will often be asked to build a service, such as a loan calculation API, that requires both mathematical correctness and clean software design.

Be ready to go over:

• RESTful Best Practices – Proper use of HTTP methods, status codes, resource naming, and payload structuring.
• Testing Strategies – Implementing a robust testing pyramid, including unit tests for business logic and integration tests for API endpoints.
• Domain Modeling – Creating clear, cohesive domain entities that accurately represent business concepts without overcomplicating the codebase.
• Advanced concepts (less common) – Domain-Driven Design (DDD) principles, custom validation frameworks, and reactive programming paradigms.

Example scenarios:

• Implementing a robust error-handling mechanism that returns clear, standardized JSON error responses to the client.
• Structuring your project using clean architecture or hexagonal architecture to separate business logic from framework dependencies.

Application Security

Security is a non-negotiable pillar of engineering at Ing Deutschland. The final stages of the interview process often place a heavy, sometimes exclusive, focus on how you design and implement secure systems.

Be ready to go over:

• OWASP Top 10 – Deep understanding of common vulnerabilities like SQL injection, Cross-Site Scripting (XSS), and Broken Object Level Authorization (BOLA), and how to prevent them.
• Data Protection – Best practices for encrypting sensitive financial data both at rest in databases and in transit across networks.
• Authentication & Authorization – Implementing secure token-based authentication systems and fine-grained role-based access control (RBAC).

Example scenarios:

• Explaining how to safely store and rotate API keys, database credentials, and secrets using modern vault solutions.
• Discussing how you would design a secure logging mechanism that prevents the accidental exposure of sensitive customer data (such as credit card numbers or passwords) in application logs.

System Architecture & Java Ecosystem

As a Software Engineer, you need to demonstrate that you can build systems that are not only secure and correct but also scalable and resilient under heavy load.

Be ready to go over:

• Spring Boot Ecosystem – Deep familiarity with Spring Boot, Spring Security, and Spring Data, as these are central to the Ing Deutschland tech stack.
• Microservices Patterns – Service discovery, API gateways, circuit breakers, and distributed tracing in a microservices environment.
• Database Management – Optimizing database queries, managing transactions, and ensuring data consistency across distributed systems.

Example scenarios:

• Designing a system that can handle a sudden spike in loan application submissions without degrading the performance of other banking services.
• Explaining how to implement a reliable message-queue system (e.g., Kafka or RabbitMQ) to handle asynchronous task processing securely.

As a Software Engineer at Ing Deutschland, your day-to-day work will involve a mix of hands-on coding, architectural design, and collaborative problem-solving. Understanding these responsibilities will help you align your interview answers with the actual needs of the team.

You will be responsible for designing, developing, and deploying high-performance backend services that power the bank's core financial products. This includes writing clean, maintainable Java or Kotlin code, creating robust RESTful APIs, and ensuring your services integrate seamlessly with existing banking systems. You will play an active role in modernizing the technical landscape, which often involves migrating services to cloud-native architectures and optimizing microservices for better scalability and resilience.

Collaboration is a key part of the role. You will work closely with cross-functional teams, including product owners, UX designers, QA engineers, and security specialists, to refine requirements and deliver high-quality features. Additionally, you will participate in code reviews, share technical knowledge with your peers, and contribute to maintaining a high standard of engineering excellence across the organization. Security compliance, continuous integration, and automated testing will be embedded in everything you build.

To be competitive for the Software Engineer position at Ing Deutschland, you need to demonstrate a strong technical foundation and a collaborative mindset. The ideal candidate combines deep backend expertise with a disciplined approach to software delivery.

• Must-have skills – Strong proficiency in Java or Kotlin, extensive experience with the Spring Boot framework, and a proven track record of designing and building secure RESTful APIs. You must also have solid experience with SQL databases, unit testing frameworks, and Git-based workflows.
• Nice-to-have skills – Experience working in the fintech or banking sector, familiarity with cloud platforms (like AWS or Azure), hands-on experience with containerization (Docker, Kubernetes), and knowledge of message brokers such as Apache Kafka.
• Experience level – Typically, candidates should have several years of professional software engineering experience, with a strong emphasis on building backend systems at scale.
• Soft skills – Excellent communication skills in English, a proactive attitude toward problem-solving, the ability to work effectively in agile teams, and a openness to giving and receiving constructive feedback.

Q: What is the typical tech stack for a Software Engineer at Ing Deutschland? A: The core backend tech stack is heavily centered around Java and Spring Boot, with some teams also utilizing Kotlin. For data storage, relational databases like PostgreSQL are common, alongside message brokers like Kafka for event-driven architectures.

Q: How difficult is the take-home coding challenge? A: The challenge itself is of average difficulty, typically focusing on designing REST APIs for financial calculations, such as loan repayments. However, the evaluation is highly rigorous, focusing heavily on clean code principles, test coverage, and security.

Q: How long does the entire interview process usually take? A: The process can take anywhere from three to six weeks. While the steps themselves are straightforward, candidates sometimes experience delays in communication between stages, so it is important to stay proactive and follow up with your recruiter.

Q: Is German language proficiency required for this role? A: No, the primary working language for most engineering teams, especially in hubs like Berlin, is English. However, having basic German skills can be beneficial for navigating daily life and general company communications.

Q: What is the hybrid work policy at Ing Deutschland? A: Ing Deutschland generally offers a flexible hybrid working model, allowing engineers to balance working from home with collaboration days in their local office (such as Berlin or Frankfurt).

To maximize your chances of success during the Ing Deutschland interview process, keep these practical, insider tips in mind:

• Be proactive with communication: Candidates have occasionally reported delays in receiving feedback after submitting the coding challenge. Do not hesitate to send a polite follow-up email to your recruiter if you have not heard back within a week.

• Prioritize security in your code: When completing the take-home task, go beyond basic functionality. Implement input validation, secure error handling, and ensure no sensitive data is exposed. Mentioning these security choices in your code comments or readme file will immediately set you apart.

• Double-check your financial math: If your task involves calculations like loan interest, ensure your logic is mathematically correct and handles edge cases (such as zero or negative inputs) gracefully. Financial precision is highly valued.

• Be prepared for rigorous code reviews: The engineers reviewing your code hold high standards. If they point out areas of improvement during the follow-up interview, accept the feedback constructively, explain your original reasoning clearly, and discuss how you would implement their suggestions.

Securing a Software Engineer position at Ing Deutschland is an exciting opportunity to build secure, high-impact financial technology that affects millions of users daily. The role demands a high level of technical craftsmanship, a deep commitment to application security, and the ability to design robust backend systems. By focusing your preparation on clean code, RESTful API design, and secure coding practices, you can navigate the interview process with confidence.

As you prepare for your interviews, remember to treat the take-home coding challenge as a true representation of your production-ready work. Focus on thorough testing, clear architecture, and robust error handling. Use the technical follow-up stages to showcase not just your coding skills, but also your ability to communicate complex technical ideas and collaborate effectively with a team of professional peers.

To gain deeper insights into compensation and help align your expectations, you can review the typical salary ranges for this role.

The compensation data reflects the competitive market rates for experienced engineers in Germany. When preparing for offer discussions, consider your overall experience level, technical depth, and the value you bring in terms of security and architectural expertise. For more real-world interview insights, detailed company reviews, and preparation resources, continue exploring Dataford to ensure you are fully equipped for every stage of your hiring journey. Good luck!