73 backend developer interview questions for hiring a pro

73 backend developer interview questions for hiring a pro

73 backend developer interview questions

It’s not only technical skills that are important when hiring a backend developer. Applicants must demonstrate that their values, soft skills, and experience all match your organization’s expectations, too. How can you review these skills in addition to their technical expertise?

If you need to know whether they can understand the functionalities of frameworks such as Express.JS, you can use our Express.JS test. But beyond this, the right set of interview questions can point you in the right direction and help you hire a talented backend professional.

We’ve got 73 backend developer interview questions to help you hire a pro. 

Take a look below and build your list to interview candidates with confidence.

Table of contents

18 backend developer interview questions to evaluate your applicants’ skills

18 backend developer interview questions for applicants

The 18 backend developer interview questions in this section are ideal for evaluating your candidates’ experience, checking whether it aligns with your requirements, and reviewing their overall knowledge. 

Ask your candidates some of these questions to see whether they can be a good fit for your open position. 

  1. Name three essential technical backend skills.
  2. Name three vital soft skills related to backend development.
  3. Should backend developers understand frontend technologies?
  4. Should backend developers understand version control systems like Git?
  5. Describe your experience using tools such as MongoDB and MySQL.
  6. Name three essential responsibilities of a backend developer.
  7. Do you think any programming language is superior for backend development?
  8. List two successful businesses that use Python.
  9. What is the difference between object-oriented and functional programming languages?
  10. Explain the key factors you think contribute to the success of development projects.
  11. What should determine the choice of programming language: the project’s use case or your proficiency with it?
  12. Why have you applied for this backend developer role?
  13. Describe your general backend development experience.
  14. What was your main motivation for becoming a backend engineer?
  15. Is feedback important to you as a backend developer?
  16. Are soft skills essential to you as a backend developer? Why?
  17. Name a time you found it challenging to finish a project. How did you complete it?
  18. What are your goals, and what do you want to achieve within the next five years in your career?

7 general backend developer interview questions and answers to assess candidates

7 general backend developer interview questions and answers

Below, you’ll find the seven most important general backend developer interview questions, along with our sample answers to help you review your candidates’ responses. 

1. Name three vital soft skills related to backend development.

Soft skills are critical for backend development, so it’s essential to know if your applicants can give examples of key soft skills.

Three vital soft skills your applicants may mention when responding to this interview question include communication, time management, and empathy. 

Top candidates will know that all three skills help backend developers deliver the right applications on time and according to a client’s specifications. 

You can assess your applicants’ time management skills and communication skills with a Time-management test and a Communication test.

2. Should backend developers understand version control systems like Git?

The short answer is: Yes, backend developers should understand version control systems like Git. Your applicants may explain that version control systems ensure developers can track the changes they make to documents or files. 

Git is the most popular system out there and your applicants will likely have experience with it. Seasoned backend developers may list a few other examples of version control systems, such as SVN and Mercurial, and explain the advantages of each. 

3. Are soft skills essential to you as a backend developer? Why?

Soft skills are fundamental for backend developers, and your applicant should recognize their importance. Candidates may explain that while technical skills are essential, team members’ soft skills enable the smooth running of projects. They may mention that soft skills help all team members work together and solve complex issues seamlessly.

4. List two successful businesses that use Python.

Your company may want to follow in the footsteps of successful businesses using Python for backend projects. Your next hire can make it happen if they understand which businesses use Python and especially how they have integrated it into projects. Two successful businesses that use Python include Uber and Spotify. 

Can your applicants explain how Python has helped these businesses achieve successful results? Do these businesses inspire them, and can they use this inspiration to help yours achieve excellent results?

5. What should determine the choice of a programming language: the project’s use case or your proficiency with it?

Even though this might seem like a trick question that requires applicants to choose one or the other, both of these factors are important. Applicants responding to this backend engineer interview question should know that both their proficiency and the use case will determine which programming language to use.

6. What is the difference between object-oriented and functional programming?

There’s one critical difference between object-oriented and functional programming that your applicants may mention. While object-oriented programming requires developers to use objects and methods, functional programming relies on variables and functions. 

Another difference between these two methods is that functional programming begins with diagrams of use cases while object-oriented programming begins with the object and class identification.

7. Do you think any programming language is superior for backend development?

Plenty of programming languages are a good fit for backend development, so each applicant may respond with a different answer to this interview question. 

However, as long as your applicant can explain the advantages of their chosen programming language, this is a sign that they have the required experience. For instance, applicants may mention that they prefer Ruby on Rails to Python when building commercial applications and explain why. 

23 backend developer interview questions related to definitions

23 backend developer interview questions on definitions

This section's 23 backend engineer interview questions are related to definitions and technical knowledge. Ask your developers these questions to review their technical expertise.

  1. What is meant by API? How do APIs contribute to application development?
  2. What is meant by data structures? List four examples of different data structures.
  3. What is a server, and what is their role in backend development?
  4. Define high cohesion.
  5. Define loose coupling.
  6. Define refactoring.
  7. Explain what OOP means in the context of backend development.
  8. Explain what array operations are.
  9. Define list functions.
  10. Explain what hash trees are.
  11. What is an algorithm?
  12. Can you explain what REST means? How does it relate to backend development?
  13. Can you name four different types of NoSQL databases?
  14. Explain the WHERE clause.
  15. Explain the HAVING clause.
  16. What is TLS and how does it work?
  17. Define YAGNI in the context of backend development.
  18. Define KISS in the context of backend development.
  19. Explain how YAGNI and KISS are different in the context of backend development.
  20. Explain what backend development means.
  21. Explain what a database is.
  22. Explain what layered architecture means in backend application development.
  23. What is meant by the API Gateway pattern?

5 backend developer interview questions and answers related to definitions 

We’ve selected five of the most important from the previous question and listed them below, along with sample answers to guide you in reviewing your applicants’ knowledge. 

1. Explain what layered architecture means in backend application development.

Coding in the backend requires a structure, which is why layering is critical in backend application development. 

Can your applicants explain that a layered architecture is free from boilerplate code or irrelevant abstractions? Can they list a few layers that layered architectures normally feature, including a controller, service, or repository layer? 

2. Can you name four different types of NoSQL databases?

There are a few essential examples of NoSQL databases that seasoned backend developers will recognize. Your applicants may have used some of the following NoSQL databases in their recent projects:

  • Graph NoSQL databases
  • Key-value NoSQL databases
  • Document-oriented NoSQL databases
  • Column-oriented NoSQL databases

Can your interviewees explain what each of these NoSQL databases does? Can they explain that NoSQL databases help solve the complexity of handling big data and provide a few advantages of the examples they gave? 

3. Explain what a database is.

Backend databases are places where backend developers store vital data. 

Applicants may know that a developer can query the data through a separate application. They may also know that by querying the data, a developer can manipulate or use it as required for a project and that applications interact with databases via a connection such as a client-side driver library.

4. Explain what backend development means.

Although this seems like a straightforward interview question, it’s also a critical one. 

Any candidate serious about joining your company as a backend developer should know that backend development involves working on server-side software. They must know that the software contains all the ‘invisible’ workings of an application or website. 

Skilled backend developers may also mention that backend developers work to ensure that websites and applications run effectively.

5. What is meant by data structures? List four examples of different data structures.

Can your applicants explain that data structures are critical in organizing and manipulating data? Are they aware that data structures are specialized formats backend developers can use to process and retrieve data?

22 backend developer interview questions related to situational and technical skills

22 backend developer interview questions situational and technical

The 22 backend engineer interview questions in this section are related to technical skills and will test how your interviewees solve complex backend challenges.

Ask your candidates some of these questions to gain a deeper understanding of their skills.

  1. In which situation would you use JavaScript?
  2. If you had to debug a program, which method would you use?
  3. In which situation is refactoring important?
  4. Describe your process for delivering negative feedback to team members.
  5. Have you ever found it difficult to agree with a co-worker’s suggestions?
  6. What is the relationship between backend development and frontend work?
  7. In which situation would you use a functional test?
  8. In which situation would you use an acceptance test?
  9. When would you consider using microservices architecture?
  10. Describe a situation where you would use clustered indexes.
  11. Describe a situation where you would use non-clustered indexes.
  12. Which method would you use to build a scalable software program?
  13. Which steps would you follow to conduct successful performance testing?
  14. How would your engineering manager rate your Python skills?
  15. Name some projects in which you recently used PHP-related skills. Describe your experience and the project.
  16. How would you rate your Git knowledge?
  17. Name some projects in which you recently used SQL-related skills.
  18. How would you rate your knowledge of the Java programming language?
  19. Have you used the Spring framework in any recent projects? Describe your experience and the project.
  20. How familiar are you with the PostgreSQL database?
  21. Describe some projects for which you used the Oracle database.
  22. How would you rate your Apache server knowledge?

5 situational and technical backend interview questions and answers

In this section, we’ve selected five of the most important questions from the list above and have provided our simple answers. This way, you can easily review your applicants’ responses and assess their technical knowledge and situational judgment. 

1. If you had to debug a program, which method would you use?

There are particular steps involved with debugging a program’s backend code. 

Your applicants may explain that they’d first run npm run start:inspect from the command line interface after going to the project directory. 

They may then enter the chrome://inspect URL after opening Chrome. After clicking the link to run the Express app and waiting for the DevTool to connect to the Express app, your applicant may then explain that they’d add several breakpoints to the file and inspect.

Another method may include diagnosing issues using the Profiler tool or checking for performance bottlenecks

To perform these checks, developers may select the Profiler tab in the DevTools console, select record, open a Chrome window, and go to the page they wish to profile. They may then wait until the log activity completes, stop the recording, and check the recorded profile to view the performance issues in a graph format.

2. In which situation is refactoring important?

Refactoring is critical if a backend developer wants to enhance the internal code by implementing small alterations but doesn’t want to alter the external behavior. Candidates may know that refactoring is vital for enhancing software’s design or structure and improving the readability of the code.

3. In which situation would you use a functional test?

If a developer wants to test a software application’s functions, they may want to use a functional test. Skilled applicants should know that developers can use black box testing to perform a functional test.

4. In which situation would you use an acceptance test?

Backend developers perform user acceptance tests at the final stages of projects. Applicants should know that organizations arrange tests before their client accepts the software. Using this approach after unit testing is the best way for engineers and developers to ensure the code works as it should.

5. How would you rate your knowledge of Java?

Does your applicants’ knowledge of Java match your requirements? To prove this expertise, they may talk about a project they’ve completed using Java. They may have several side projects in their portfolio in which they used Java, too.

Look for evidence that they have experience with Java and are always working on improving their skills. You can also review their Java skills with one of TestGorilla’s Java tests, too. 

10 backend developer interview questions related to soft skills

10 backend developer interview questions soft skills

The 10 backend engineer interview questions in this section are ideal for reviewing your applicants’ soft skills. Ask your applicants these questions to thoroughly assess their non-technical abilities.

  1. How would you rate your communication skills, and how do you communicate technical ideas with other teams?
  2. How would your engineering manager rate your problem-solving skills?
  3. How well do you manage your time? How would your manager rate your time-management skills?
  4. Do you consider attention to detail an essential skill for backend development? Why?
  5. How essential are strong teamwork skills for backend developers?
  6. Describe the values that help you complete challenging projects. 
  7. How would your engineering manager rate your critical thinking?
  8. Do you consider project-management skills essential for backend developers? Why or why not?
  9. Is empathy an essential skill for backend developers? How have you used it in your work with clients?
  10. Why is adaptability a fundamental soft skill for backend developers?

5 backend developer interview questions and answers related to soft skills

Below, you’ll find answers to the five most important questions about soft skills in backend development. Use them to review your interviewee’s responses and assess their knowledge.

1. Do you consider attention to detail an essential skill for backend development? Why?

Candidates should know that attention to detail is critical for backend developers. They should be aware that the code they write must be clean and error-free to ensure their application works efficiently. 

2. Do you consider project-management skills essential for backend developers? Why or why not?

Although backend-development projects are usually incredibly complex, having strong project-management skills helps backend developers control three essential factors of their work: delivering projects on time, within scope, and within budget.

Even though backend developers aren’t usually project managers and don’t have the same background, having sufficient project-management knowledge can help them handle challenging projects successfully. Is your applicant able to give some examples where this was the case? 

3. How well do you manage your time? How would your manager rate your time-management skills?

Delivering a backend-development project within a certain time frame requires top time-management skills. 

Look for candidates who can explain how they manage their time when working on different projects. 

For instance, do they track their time with the help of a software tool like Toggl? Do they handle repetitive tasks by writing scripts? Do they delegate jobs that they can’t complete? You can also further assess their ability to manage their time well with our Time-management test.

4. Is empathy a vital skill for backend developers? How have you used it in your work with clients?

Applicants should know the importance of empathy for backend development. They may explain that only by understanding the users that will use their software can a backend developer fully understand the project’s requirements. 

Do your applicants try to understand the user’s needs and pain points? Do they put themselves in the user’s position to try to figure out exactly what they need? Some backend developers might even go as far as to talk to users to fully grasp what they are looking for.

5. How would your manager rate your problem-solving skills?

Since problem solving is critical for backend engineers, look for applicants whose managers would rate their problem-solving skills highly and can prove it with an example. 

For instance, your applicant may have worked on a complex project for which they broke down the main problem into smaller, easier-to-tackle parts. If you need to evaluate your applicants’ problem-solving skills, consider our Problem-solving test.

At which stage should you use these backend developer interview questions?

back-end developer dictionary definition

The best moment to use the interview questions from this article – or any interview questions, for that matter – is after your applicants complete a skills assessment.

This way, you’ll be able to easily shortlist the best ones based on the results and only spend time with them in the next stages of the hiring process.

Using this method means your hiring process will be:

  • Bias-free and objective
  • Faster and more effective
  • More cost-efficient

You’ll even know which follow-up interview questions to ask your candidates based on the results from their skill assessment.

Find the best programmers with our interview questions for backend developers 

We know that assessing backend experts for your organization isn’t easy. Still, the best approach is to integrate skills assessments into your hiring process and use the right interview questions for backend developers. 

For the best results, we advise you to use a skills assessment that features the right technical skills tests, such as our Express.JS test, to identify the most capable backend engineers in your talent pool. You can also use cognitive-ability tests to evaluate your candidates’ soft skills and make sure they would be a good fit for the role.

Then, invite your top applicants to an interview to further assess their skills with the help of our interview questions above. This way, you’ll be able to shorten and simplify your hiring process and make the best decision with confidence and ease. 

Find the best backend developers for your organization with the help of TestGorilla’s skills assessments and our interview questions. Eliminate stress and bias from your recruitment process, starting today. 

 Get started for free today and start making better hiring decisions, faster and bias-free.

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