150 Common Back-End Developer Interview Questions

Are you a back-end developer? Is your company looking to expand your development team? Either way, being prepared for the back-end developer interview process is imperative. So, to help, we’ve compiled this list of 150 back-end developer interview questions that hiring managers and job candidates can use to prepare for a tech interview.

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In this post you’ll find:

  1. General Interview Questions for Back-End Developers
  2. Interview Questions About Programming Languages, Logic & Algorithms
  3. Interview Questions About Database Administration and NoSQL Databases 
  4. Interview Questions About Design Patterns and Code Design
  5. Web Development Interview Questions 
  6. Security Interview Questions

General Interview Questions for Back-End Developers (#1-25)

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  1. Can you describe your current career trajectory?
  2. Why are you interested in this position?
  3. What is your favorite programming language?
  4. Can you describe your favorite development project to date?
  5. What defines a successful project?
  6. What is your experience with java programming?
  7. How many back-end development teams have you worked on?
  8. Can you describe the difference between HTTP protocol and TCP?
  9. Tell us about a time when a project did not succeed. What did you do to correct it? Or, what would you do differently to ensure it is a successful project?
  10. What is your favorite aspect of back-end development?
  11. Are you up-to-date with the latest technologies in back-end development?
  12. What do you enjoy about a remote work environment?
  13. How well do you collaborate with front-end developers?
  14. Can you describe your experience with security in the development environment?
  15. How do you deal with negative feedback when you receive it?
  16. Do you feel comfortable acting as a leader and delivering negative feedback to a colleague?
  17. What operating systems do you prefer to work with?
  18. Can you describe your coding skills and experience?
  19. What is your preferred working style?
  20. What is it about our company values that stand out to you?
  21. What new web development skills do you wish to hone in the near future?
  22. Can you describe your leadership experience?
  23. Do you prefer to work virtually or face-to-face?
  24. Can you provide insight into what makes a strong back-end development team?
  25. Why should we hire you over other back-end developers?

Interview Questions About Programming Languages, Logic, and Algorithms (#26-50)

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  1. Can you describe three issues with your preferred programming language?
  2. What are your favorite aspects of your preferred language?
  3. What is your understanding of functional programming?
  4. Can you explain what high-order functions are and what they are useful for?
  5. What are the issues with Java? Why do some software developers dislike Java?
  6. What is the primary function of a namespace?
  7. Can you list an alternative for a namespace?
  8. What is a defragger? Explain how you would design a defragger utility.
  9. What approach would you use to sort a 15GB file? What about a 15TB file?
  10. Have you ever written a garbage collection system?
  11. Using your preferred language, write code for a program that can generate random mazes.
  12. What is stack overflow?
  13. What is your experience with problem-solving with different programming languages?
  14. Can you explain what a closure is and what it is useful for?
  15. What is a generic and what can it be used for?
  16. What is your opinion on static-type systems?
  17. What are your thoughts on dynamic type systems?
  18. What is a stack and how is it different from a heap?
  19. What is your opinion of Node.js? Do you have experience using this language?
  20. Write a high-order function in your preferred programming language.
  21. When it comes to programming, what does it mean when functions are referred to as “first-class citizens”?
  22. Can you explain the interoperability between C# and Java?
  23. Write a referentially transparent function.
  24. Write a function that is referentially opaque.
  25. Are you familiar with pattern matching?

Interview Questions About Database Administration & NoSQL Databases (#51-75)

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  1. Explain what you understand about NoSQL databases.
  2. Describe your process for migrating an application from one database to another?
  3. Can you tell us how you would manage database schema migrations?
  4. What is lazy loading?
  5. When is lazy loading useful and how would you utilize it?
  6. What do you know about ACID (atomicity, consistency, isolation, and durability)?
  7. What is the “N + 1 problem” and how can one fix it?
  8. Can you describe what is needed to utilize database normalization?
  9. What is a denormalized database and when would you use one?
  10. Can you name the different types of NoSQL databases?
  11. Can you describe eventual consistency in terms of NoSQL databases?
  12. What is your opinion of the growing interest in NoSQL?
  13. Do you know what the CAP theorem is?
  14. Why is NoSQL good for scalability?
  15. How do you scale vertically?
  16. How do you scale horizontally?
  17. What is the difference between scaling vertically and scaling horizontally? Discuss the benefits of both techniques. 
  18. Can you describe the difference between NoSQL databases and RDBMS (relational database management systems)?
  19. Do you know what sharding is?
  20. What is a column-oriented NoSQL?
  21. What is document-oriented NoSQL?
  22. What does key-value mean in the context of NoSQL?
  23. What is the use of transactions in NoSQL databases?
  24. Can you describe how you would automate changes to the database schema?
  25. What do you know about the technique called blue/green deployment and how it functions?

Interview Questions About Design Patterns and Code Design (#76-100)

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  1. Can you discuss Inversion of Control and how it can be used to improve the design of code?
  2. What is your understanding of the Law of Demeter?
  3. Do you know what a Data-Mapper design pattern is and how it functions in comparison to an Active-Record design pattern?
  4. What is your opinion on inheritance vs composition as it relates to object-oriented programming?
  5. What is the primary function of an anti-corruption layer?
  6. What is the DRY (don’t repeat yourself) principle? Describe it.
  7. Write code that deliberately goes against the DRY principle then show us how you’d fix it. 
  8. What is dependency injection when it comes to software engineering?
  9. Do you have an in-depth understanding of the design principle called Separation of Concerns? Can we discuss this topic in detail?
  10. When it comes to object-oriented design, what is loose coupling? And why is it important to object-oriented design or code design? 
  11. How does test-driven development influence code design?
  12. Can you explain the difference between coupling and cohesion?
  13. Why is important to have high cohesion and loose coupling?
  14. What is refactoring? How would you use refactoring?
  15. As a back-end developer, can you explain the difference between design and architecture?
  16. In test-driven development or TDD, tests are often written before code. Do you agree with this procedure? If so or if not, please explain. 
  17. Why is object-oriented design so popular in the development industry? As a back-end developer, can you explain why you think it dominates the market? 
  18. How do you assess if the code you’ve written has a design flaw?
  19. Array indexes start with 0 in most programming languages. Why is that? Can you explain?
  20. Explain what data abstraction is.
  21. Provide an example that violates the principles of data abstraction then explain how you would fix it. 
  22. What is your opinion on code comments? Do you find them to be useful or unnecessary?
  23. What would you consider to be a bad design?
  24. Do you have a thorough understanding of domain logic in stored procedures? If so, can you discuss the pros and cons of it?
  25. How would you provide constructive criticism to a fellow development team member who was struggling with a project? 

Web Development Interview Questions (#101-125)

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  1. What are first-party cookies?
  2. Can you explain what third-party cookies are? 
  3. Can you discuss how you would manage a web service API versioning?
  4. What is a stateless code and what are the benefits of having stateless services?
  5. When would you consider stateless code to be bad?
  6. When it comes to web development for back-end developers, it is common to use Model-View-Controller and Model-View-Model approaches. Can you explain what they are?
  7. Can you discuss your approach to debugging?
  8. How can you deal with broken code?
  9. In the development environment, it’s important to collaborate. Explain your experience(s) working on web development projects with multiple people. 
  10. Do you enjoy writing code?
  11. Can you explain the advantage of using HTTP/2 over HTTP 1.1?
  12. Provide a description of CORS (cross-origin resource sharing) and explain why it is important.
  13. What is a webpack?
  14. What is the difference between a span tag and a div tag when using HTML 5?
  15. Besides local storage, what is another type of web storage?
  16. What is a document object model and how is it used?
  17. Can you explain your experience with pair programming?
  18. As a back-end developer, what problem-solving skills do you bring to the table?
  19. Discuss the difference between an SVG (scalable vector graphic) tag and a canvas tag in HTML 5. 
  20. When it comes to JavaScript, what is type coercion?
  21. Can you describe how you would integrate different stylesheets into a single website?
  22. As a back-end developer, what would you recommend for optimizing the loading time of web applications?
  23. How can you reduce the number of redirects on a website?
  24. Explain your understanding of NPM (node package manager). 
  25. Besides the prompt box, what are other types of popup boxes that are available in JavaScript?

Security Interview Questions (126-150)

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  1. Do you know how to write code that is secure?
  2. In your opinion, is it the duty of the back-end developer to make sure the code is secure?
  3. Can you explain what 2FA or two-factor authentication is?
  4. Describe how you would implement two-factor authentication in existing web applications.
  5. Is it possible to detect SQL injection via a static code analysis? 
  6. What is your understanding of a cross-site forgery attack?
  7. Can you explain how HTTPS works in general?
  8. Can you explain how HTTPS helps protect against attacks?
  9. Do you know what a man-in-the-middle attack is?
  10. Can you explain how to prevent a user’s session from being stolen?
  11. What is cookie hijacking? 
  12. How do you deal with logs containing personally identifiable information or other sensitive data?
  13. What is your understanding of cryptography?
  14. What is the difference between a reverse proxy and a VPN?
  15. What is your opinion of the use of VPNs?
  16. When it comes to software development, is there any way to ensure your web application is 100% secure?
  17. How would you approach solving an internal server error that caused security concerns?
  18. This job description mentions that the preferred candidate has a deep knowledge of security. Do you believe that you are qualified?
  19. How would you use strong leadership skills to lead a discussion on the importance of web security? Explain the topics that you would cover in a hypothetical presentation. 
  20. How do you ensure that your personal websites and web applications are secure?
  21. Do you believe companies should have a person solely dedicated to securing their web assets?
  22. How would you collaborate with front-end developers to ensure that a website is secure?
  23. Can you explain what data encryption is and its importance?
  24. Describe the difference between hashing and encryption algorithms.
  25. What are the pros and cons of using symmetric encryption?