CodeSubmit Interview Series

The 9 Best Backend Developer Interview Questions in 2023

Want to hire your next backend developer? Then, you need the right backend developer interview questions. Here are the 9 top interview questions to help you identify your next team member. Read on!

Interviewing backend developers 

Backend developers make use of the technology that is required to develop products for the backend of a website. They often focus on things like website architecture, databases, backend logic, APIs, and servers. 

Typically, backend developers use different tools, languages, and frameworks. Some of them are JavaPHPRubyNodeJS.NET, MongoDB, MySQL, and Oracle.

If you're looking for your next developer, look no further. Here are the 9 best backend developer interview questions to ask. 

Beginner backend interview questions

What interview questions can you ask junior backend developers? Junior developers have limited technical knowledge, so don’t focus too much on their technical ability, but rather on their understanding of backend development. Here are our top backend developer interview questions.

1. What skills do you think a backend developer should have? 


There’s no right or wrong language for backend developers. However, there are some popular object-oriented programming languages (such as Python, .NET, and Java) and functional programming languages (such as Clojure, Haskell, Ruby on Rails, and SQL). 

Listen to why your candidates are using a specific language. How can they use this language to improve your product? 

Other skills include APIs, data structures, servers, and algorithms. 

2. What is the largest web app you’ve worked on? What was your area of responsibility? 


This is a great question to use if you want to dive deeper into candidates’ work. For instance, even if a developer has listed a project as their work experience, you might not know what their role was as part of that project. With this question, you get a better understanding of how they work in a team, their workflow processes, and more.

3. How well do you know and use object-oriented programming (OOP)? 


Understanding how well candidates know object-oriented programming languages or OOP will help you determine if they’re a good fit for your company. OOP is the general practice when organizing code because it helps generalize and objectify groups of code and apply them in different situations. The alternative is procedural programming, which means that the organization of code focuses more on action than object.

4. How do you approach debugging and improving applications? 


Debugging and troubleshooting are key for the development lifecycle. This question helps you understand how candidates approach the troubleshooting process and how they’ll handle updates and upgrades of existing applications and programs. 

Look for how they lay out their process, the tools they use, and how well they understand how these steps help your overall business goals. 

For instance, candidates may offer the ideal process they’d use. First, they’d need to try the basic solutions and collect the necessary information such as pictures and videos that can be used to debug. Second-level support can include checking Application and Network Performance Monitoring tools to see CPU, memory, code-level performance, web services, caches, logs, databases, and so on. And any changes should be followed by a change management process. Monitoring tools should be checked daily to detect faults before they escalate. 

5. How would you improve page performance?


To improve page performance, you should clean up the HTML document, minimize external HTML requests, use compressed and smaller images, as well as sprites, include JavaScript at the bottom of the page, optimize HTML, JavaScript, and CSS, use caching and CDN.

Senior backend developer interview questions

What are some senior backend developer interview questions? These questions will help you understand your candidates’ technical skills. 

6. What are the advantages of using microservices architecture? 


A backend developer should be able to determine when a certain architecture should be used. Microservices architecture is defined by the integration of many small independently deployable services into one, single application. This setup improves versatility; individual services can be written in different programming languages. In other words, you leverage the strengths of every language for the requirements of the services. 

The services also remain loosely coupled, which ensures easier maintenance. Larger teams see the microservices architecture model as effective, even though there can be challenges with, for example, debugging. 

7. How do you manage API versioning? 


Versioning is an important part of API design. It gives developers the ability to improve their API without having to stop applications when new updates are rolled out. The types of versioning are: 

  • URL versioning or route versioning (URI routing is used to point to a specific version of the API)

  • Versioning with a custom header (REST APIs are versioned with custom headers with the version number included as an attribute)

  • Query String Parameter (the version number is included as a query parameter; however, this isn’t typically the recommended method)

8. What are CSS Sprites? 


Each image sends out an HTTP request separately. That means that a web page with a high number of photos takes longer to load. CSS sprites decrease the number of HTTP requests by minimizing the loading time of a web page by combining multiple small pictures into a single image. 

9. How do you find the most expensive queries in an application?


Database queries that execute slowly or utilize large amounts of CPU/memory resources are called expensive queries. They’re the most common performance issue caused in an application. To find these queries, SQL Activity Monitor is an easy and rich UI tool within the SQL Server Management Studio. Alternatively, you can use SQL Dynamic Management View (DMW). 

Over to you!

That’s it, these are the 9 best backend developer interview questions. 

Not only do you want to hire someone who has solid technical knowledge, but they should also understand the principles of backend development; how they can improve your processes and achieve your business goals. 

Your interviews are a great place to get an understanding of who your candidates are. But how do you assess their technical skills? 

Try CodeSubmit’s technical assessment tests. Get started with a free trial (no credit card required).