Back-End Developer Interview Questions

Any business that is dependent on technology and has a user-facing website or application needs a back-end developer. The job of a back-end developer is to maintain the various databases and prepare all the information on the server to power the client-facing side of the website/application. This includes looking after core application logic, data and application integration, and API. 

Needless to say, back-end developers are in great demand right now. Given that a vast majority of businesses have moved online to keep up with challenges posed by the pandemic, the need for highly specialized people who can harness the technology and keep things running is like never before. It’s not surprising that the hiring of specialized engineers such as back-end developers is expected to follow an upward trajectory. 

Now comes the challenging part -- to get hired as a back-end developer, you need to ace the back-end developer interview questions. If you are preparing for a tech interview, check out our technical interview checklist, interview questions page, and salary negotiation ebook to get interview-ready! 

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This guide has been created to help you prepare for a back-end developer interview. We will discuss:

  • What skills should back-end developers possess?
  • Roles and responsibilities of a back-end developer
  • Technical topics to prepare for your back-end developer interview
  • Top 25 interview questions for back-end developers
  • Back-end developer interview questions -- FAQs

What Skills Should Back-End Developers Possess?

Here’s a breakdown of the core skill set of every developer looking to ace the back-end engineer interview questions:

  • Knowledge of relevant back-end programming languages
  • Thorough understanding of front-end technologies such as HTML and CSS to ensure seamless integration
  • Proficiency of version control systems such as Git
  • Managing database administration and scaling applications 
  • Knowledge of data structures, APIs, and algorithms
  • Experience in working with tools such as MySQL, MongoDB, Oracle, and SQL server

Roles and Responsibilities of a Back-End Developer

While the exact responsibilities may vary depending on the company’s business, below is a snapshot of what to expect:

  • Working with the front-end developers on  server-side logic and outward-facing web application elements
  • Optimizing the applications for maximum speed and scalability
  • Designing data storage solutions 
  • developing content management system and maintaining the same
  • Working on cloud computing integration
  • Troubleshooting and debugging applications
  • Creating reusable code and libraries for future use
  • Write code and tests, build prototypes, solve issues, profile and analyze bottlenecks
  • Design robust APIs that support mobile and desktop clients

Technical Topics to Prepare for Your Back-End Developer Interview

Confused about which technical topics you need to master before you can breeze through the back-end technical interview questions? Here’s a checklist:

Back-End Programming Languages

There are two types -- Object-oriented programming languages (OOP) such as Python, .NET, and Java, and functional programming languages such as Clojure, Haskell, Ruby On Rails, and SQL. It's important to know both because different organizations use different languages for their back end. 

For example, Uber, Mozilla, and Spotify use Python, whereas AirBnB uses Ruby on Rails. If you want to crack Java back-end developer interview questions, make sure to know these programming languages like the back of your hand. 

Learn more about the Popular Back-end Development Languages to Get a Job at FAANG.

APIs

APIs serve as the medium through which data gets transferred. They act as a bridge between the back end and the databases and allows the developers to fetch the user data. Typically, most back-end developers work with Python and NodeJS to create the APIs.

Data Structures

Data structures are a fundamental aspect of organizing, accessing, and modifying data, and back-end developers need to have a thorough knowledge of the same. Popular data structures a back-end developer should know include:

  • Array operations
  • List functions
  • Hash tree
  • Tree and the related operations

Servers

Servers are the backbone of any back-end development. They work round the clock and aid in delivering essential services such as receiving requests for web-based files and transferring such files to the client. 

Back-end developers should have knowledge about deploying or hosting servers and be familiar with commonly used servers like Apache, Nginx, IIS servers, and Microsoft IIS. Proficiency of cloud-based platforms such as AWS, Heroku, Google Cloud Platform is a bonus for cracking those server-side interview questions.

Algorithms

 Any type of problem-solving in software development is dependent on algorithms. A majority of the back-end engineer interview questions test your algorithmic skills. 

That’s why back-end developers should learn about depth-first search and breadth-first search algorithms, sorting algorithms like the bubble sort, selection sort, insertion sort, merge sort, quicksort, iterative and recursive algorithms. 

Top 25 Interview Questions for a Back-End Developer

The back end of any application or website involves a communication network between various servers, browsers, and databases. As a back-end developer, it is your job to ensure seamless communication between these components so that the user-facing side performs as expected. 

Regardless of the company where you interview, you can expect the back-end engineer interview questions  to be classified into three buckets:

  • Technical questions to test your acumen
  • Behavioral questions to test how you have performed in the past
  • Questions about your soft skills to assess your cognitive skills 

Here are some sample questions to help you to nail your interview prep:

Technical Back-End Developer Interview Questions

If you are a beginner back-end developer, most of the back-end engineer interview questions will evaluate your basic understanding of different programming languages. If you are a mid-level back-end developer, be prepared to get grilled on more advanced concepts about the framework of backend development. 

Lastly, if you are an advanced back-end developer, the questions will focus on why you want to work with specific frameworks, technologies, languages, etc. Here are some sample questions:

  1. What is your favorite programming language? And why?
  2. What do you understand by NoSQL databases? Explain.
  3. What is the difference between software architecture and software design?
  4. What is JavaScript, and why is it used?
  5. What is your approach to debugging?
  6. How would you find the most expensive queries in an application?
  7. What is the difference between an acceptance test and a functional test?
  8. Which sorting algorithm should you use and when? 
  9. What is the meaning of “high cohesion” and “loose coupling”?
  10. Why should you use microservices architecture?
  11. Explain the difference between cohesion and coupling?
  12. When is refactoring useful?

Behavioral Interview Questions

Unlike technical questions, behavioral questions do not vary based on your experience level. Ultimately, the interviewer is trying to evaluate your working style to check whether you are the right fit for the company. 

Here are some of the common back-end developer interview questions for the behavioral round:

  1. What is your experience with object-oriented programming (OOP)?
  2. Tell us about a time when you received criticism about your work and how you handled it. 
  3. If you have to deliver negative feedback to members of your development team, how would you do it?
  4. Tell me about your favorite development project to date and what it was like from start to finish.
  5. What is your experience with GoTo, and do you prefer structured programming?
  6. Tell me about the largest web application you have ever worked on? What coding were you responsible for?
  7. What's your preferred type of development environment?
  8. Which programming languages do you want to work with and why?

Read Behavioral Interview Questions for Software Developers for more.

Soft Skills Questions

Your soft skills are your personality traits. All questions for this segment are designed to assess your ability to work with others and grow within the organization. Check out some sample soft skills questions mentioned below:

  1. What do you think contributes to a successful project?
  2. How do you keep up with the latest technologies and trends?
  3. Tell me about a time when you had to work with someone difficult? How did you handle it?
  4. What is the most difficult change you’ve encountered in your career?
  5.  How do you handle situations where there is a lot of tension between you and a colleague?

Back-End Interview Questions -- FAQs

Q. Can a front-end developer work on back-end development?

As the name suggests, the front end is concerned with the user-facing side of an application or website. Back-end, on the other hand, is concerned with the server-side of a website or application.  While these two roles are two sides of the same coin, the roles and responsibilities are very different. In fact, a back-end developer works with a front-end developer to deliver a seamless experience to the user.

Q. Which programming language is the best for back-end development?
There is no correct answer to the question as the use case determines which language you should use. It also depends on how proficient you are with a particular programming language. 

Q. What is the average salary of back-end developers?
The salary depends on the skills you bring to the table. However, the average base salary of a back-end developer is $117,868, plus a $4,000 cash bonus per year (Indeed.com).

Are You Ready for Your Back-End Developer Interview?

Thorough preparation is the best way to nail back-end engineer interview questions and impress your interviewer. Interview Kickstart can help with your preparation!

If you need help with your prep, join Interview Kickstart’s Back-End Engineering Interview Course — the first-of-its-kind, domain-specific tech interview prep program designed specifically for back-end engineers. Click here to learn more about the program. 

IK is the gold standard in tech interview prep. Our programs include a comprehensive curriculum, unmatched teaching methods, FAANG+ instructors, and career coaching to help you nail your next tech interview. 

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