30 Backend Developer Interview Questions | You Must Know to Land a Job

I have 9+ years of experience in backend development. I have taken numerous interviews for different companies like IBM labs, NetApp, and others.

Based on my experience interviewing candidates for a backend developer role, here are very common backend developer interview questions. If you want to land a good job in product-based companies, don’t miss these questions.

So go through this complete list of questions shared here.

For the backend developer role, you have to attempt different interviews like a technical and a problem-solving interview round, a system design interview round, a behavioural and soft skill interview round, etc. For every round, you will be asked for the different set of questions.

Here, I’m listing some of the very frequently asked interview questions for the backend developer.

1. Technical Interview Questions for the Backend Developer

In the technical interview, mainly, questions are asked on topics like API development, microservice architecture, database, etc. Along with this, the interviewer will ask questions on technical topics that you have mentioned in your resume or the topics related to the listed projects in your resume.

API Related Questions

1. What is REST API? Explain the RESTful APIs concept. How do they work?
   Solution: You can find answers to all these questions in the REST API architecture.
2. How do you ensure the security of data transmitted over APIs?
3. Explain different methods used in HTTP protocol.

Here are some more RESTful API interview questions.

Architecture

4. What is the difference between a monolithic and microservices architecture? When would you choose one over the other?
5. Can you explain the process of authentication and authorization in a web application?
6. Describe the role of a web server and an application server in a web application architecture.
7. Explain client-server architecture.

It is also expected that you should have knowledge of containerization tools like Docker and Kubernetes.

Database

8. What is indexing in databases? What is the purpose of it? How does it improve query performance?
9. Explain how you can optimize a slow-performing database query.
10. What is the difference between SQL and NoSQL databases? Where will you use which type of database, explain with examples.
    Solution: Refer detailed SQL vs NoSQL database guide for the answer.
11. What is caching, and why is it important in API and web development?
12. How does asynchronous programming work? What is the benefit of it? Explain with examples.
13. There can be different SQL query interview questions, the interviewer can ask you.
14. If you are a fresher, refer to the basic SQL query concept for a job interview.

Based on your level of experience, the difficulty level of these questions varies from low to moderate to high.

2. Problem-Solving and Coding

Here you have to write the code. You can choose any programming language of your choice. Choosing a programming language as per the job requirement will be a good choice.

15. Given a list of numbers, write a function to find the sum of all even numbers.
16. Implement a basic token-based authentication system for a REST API.
17. Solve a coding problem related to data manipulation or algorithmic challenges.

I’m a professional Python backend developer. I always choose Python as my preferred programming language to solve coding challenges. If you are a Python developer, refer following links to advance in the coding round.

• Complete Python tutorial
• Python interview questions

3. System Design

18. Design a scalable backend architecture for a payment API or social media platform.
19. How would you handle it if all of a sudden traffic increases on your web application?
    Hint: Discuss different techniques like load balancing, caching, and database scaling.
20. [for experience candidate] How will you deploy the backend application in production? What tools or technologies would you need?
21. Design a database schema for an e-commerce website or shopping portal with products, categories, and user orders.

4. Behavioral Questions

22. Describe a challenging technical problem you’ve faced and how you solved it.
23. How do you approach working in a team environment? Can you give an example of a successful collaboration experience? [Team-work]
24. Talk about a time when you had to prioritize tasks to meet a tight deadline. [Project deadline achievement]
25. How do you stay updated with the latest developments in backend technologies?

5. Experience and Projects

Here, the interviewer will go through the project that you have mentioned in your resume and will start asking questions related to them.

26. Explain the latest backend project you’ve worked on (mentioned in your resume) in detail. What technologies did you use, and what challenges did you overcome?
27. How did you optimize the performance of a backend service?

6. Soft Skills

In soft skills, the candidate is tested based on communication, problem-solving ability, and adaptability.

28. How do you explain complex technical concepts to non-technical or junior team members or stakeholders? [How do you communicate?]
29. Problem-solving: When encountering a difficult bug in the production in the backend code, how will you debug it? [How’s your problem-solving skill?]
30. Can you discuss a situation where you had to quickly learn a new technology or programming language based on the project demand? [How do you adapt to the ever-growing technology?]

These are the few very common backend developer interview questions.

Aniruddha Chaudhari

I am a Python enthusiast who loves Linux and Vim. I hold a Master of Computer Science degree from NIT Trichy and have 10 years of experience in the IT industry, focusing on the Software Development Lifecycle from Requirements Gathering, Design, Development to Deployment. I have worked at IBM, Ericsson, and NetApp, and I share my knowledge on CSEstack.org.