Node.js Interview Questions to Ask a Candidate

12 min
Rogneda Kniazhina
Technical Writer
Sophia Davis
Digital Transformation Expert

Let's face it from the start: the hiring process is challenging. The modern hiring system involves several stages of interviews, which allows you to weed out those who are unsuitable, but how to choose the only one from a short list? For a few interviews, no matter how detailed and extensive they may be, it is necessary to evaluate the candidate according to several criteria, test them, and determine whether they really fit your company.

Analyze the algorithm by taking the hiring Node.js developers process as an example. We hope this article will help you: we have collected, systematized, and divided common Node.js interview questions into categories that will be useful.  Of course, it is desirable to have a technical lead or another developer who can check the technical side when hiring a new specialist, but this is not always possible. It's okay if you're not a tech genius and don't know technology thoroughly; we've specially prepared Node.js programming interview questions that will help you explore the expertise of a potential employee and allow you to understand their answers.

Types of Interview Questions for Engineers

Non-Tech Questions for Node.js Candidates

A list of general Node.js interview questions and answers for experienced and junior specialists is an essential part. They reveal the essence of the candidates as experts and as people. It is crucial to correctly formulate abstract questions to understand their values, aspirations, and views. After all, productive cooperation directly depends on the links in the chain! One of the main recommendations: do not start the interview with very narrow or specialized questions; move gradually from general to specific.

What Previous Experience Do You Have With Node.js?

This question is a test of integrity. A candidate with no actual practice in Node.js can hardly trick professional developers, and the ability to remember theoretical definitions should not be a ticket to the team. Simultaneously, this is not about performing tasks on the go with paper and pencil or in some online editor. It is always better to give a candidate some “homework” assignments to show that experience matters.

What Is, In Your Opinion, An Ideal Node.js Development Workflow?

Candidates should describe their vision of the entire process, beginning with identifying the problem and delivering code to production. Team workflow is a necessary process to define because it lets one understand how to communicate with a remote team, solve conflicts, integrate different time zones, etc. It may not be compulsory in the list of Node.js interview questions since many senior developers write JavaScript code. In general, an understanding of a team workflow is expected from seniors.

Do You Interact With Node.js Beyond Work?

It is always helpful to know how deeply candidates are interested in the technology they are working with: which relevant news channels they monitor, which open-source projects Senior Node.js developers participate in, which thematic conferences they attend, etc. A broad beyond-work experience in Node.js can add extra points to any candidate.

Name The JS-Based App Or Website That Annoys You. What Is Wrong With It, And How Would You Fix It?

Perhaps this is a trick question, but it will immediately show who is in front of you: an ardent enthusiast or an ordinary busy bee. With this question, you evaluate not only professionalism and the ability to see mistakes but also activity, the ability to find an effective solution and improve something created earlier. A proactive candidate is more suitable for agile teams.

What Is The Difference Between Mobile And Web Development?

At a time when the whole world is striving for mobility and accessibility, developers have to prioritize mobile-friendly designs, especially when it comes to web pages. The candidate should emphasize the need to optimize for all platforms and highlight the differences, such as screen size, touch input, limited multitasking, and the variation in browser plug-ins.

Can You Describe How You Handle Your Biggest Challenge?

This is a question with a dual purpose: on the one hand, you will find out how a person copes with stress, whether he can work under pressure and tight deadlines, on the other hand, how exactly he solves complex tasks on projects and whether he can think outside the box. Since there is no correct answer here and it will complicate the evaluation of the candidate, try to give examples to get as many details as possible.

Junior: Basic Node.js Interview Questions

By writing a job description, you are creating a profile of your ideal candidate, including his knowledge, hard and soft skills, experience and previous projects (industry or niche products). For the interview, you select those who can really become it. But do not rush to test everything at once; the principle from simple to complex shows much greater efficiency than a chaotic survey unless you want to try their stress tolerance this way.

Here we offer you Node.js interview questions for freshers – 1-year experienced developers. These questions will help you understand their soft skills, understand the desire to learn, and improve themselves as specialists. Naturally, beginners don't have significant experience. However, during the Node.js coding task, specialists should submit sample projects.

The questions for 1-year experienced Node.js developers are more theoretical than practical. However, novice specialists should be well aware of the basics. They should understand technical but straightforward coding concepts such as event loops and event programming during interview questions on Node.js. During the technical interview, they should clarify how coding works with Node.js and its advantage over other technologies.

What Is Node.js, And What Is It Used For?

Although the question may seem strange, it is important to check whether the candidate knows what he is working with. Node.js is an open-source JavaScript runtime based on Google Chrome's JavaScript V8 engine. Developers can indeed say that's neither a programming language nor a framework and will be correct. However, what’s it? Node.js is like JavaScript but with extended traditional functions beyond the web browser. Node.js specialists apply it for creating web applications and cross-platform mobile apps.

What Are The Advantages Of Node.js Compared To Other Technologies?

  • Multitasking: enabled by an asynchronous, non-blocking model.
  • Fast transition: a developer who has ever worked with pure JavaScript will have no problems switching to backend Node.js development.
  • Flexibility and performance: easy castability and flexibility significantly improve the performance of sites and applications that perform real-time tasks (video streaming, chat, online games)
  • Possibility of a clear full-stack development: if your product is developed with JavaScript on the front and backed with Node.js, you create a comfortable full-stack process.
  • Active support for well-known brands: Microsoft, PayPal, Amazon, Netflix, Uber, and LinkedIn create their products with Node.js.
Node.js is used by at least 30 million websites

With Node.js, you have a big chance to be a part of digital media trends with your new project.

Why, In Your Opinion, Was The V8 Engine Necessary?

A detailed response to this question may also cover some other relevant features of V8, such as the memory structure, functions of Garbage collector, and memory leaks and methods of addressing them. Someone can be confused by these questions for 1 year experienced. So, we decided to discuss the basics of V8 and it logically leads lead to the following question:

How does the Event loop work? We believe this is one of the most important interview questions on Node.js for beginners. An event loop is a framework that manages events by executing a callback function in a queue. It is responsible for its asynchronous and non-blocking I / O. It is important to know that an automatic flow is created in the event loop. It plans operations based on the specified conditions. There is only one thread, which is an event loop in Node.js that determines which thread will execute callback functions at any given time.

node js event loop flow

What are the timing features of Node.js? There are four commonly used timing features of Node.js you can ask during Node.js interview questions:

  • setTimeout / clearTimeout - can be used to delay code execution
  • setInterval / clearInterval - can be used to execute a block of code continuously
  • process.nextTick - can be used to set code execution at the beginning of the next cycle of the event loop
  • setImmediate / clearImmediate - can be used to execute code at the very end of the event loop.

What Is Event-Driven Programming?

It is a popular approach that uses events to trigger various functions. The event can be anything, for example, clicking a mouse button. When the event happens, we have a callback process, which has registered with the element, following the "publish-subscribe" pattern. Thanks to this flexible approach, Node.js is more productive than other technologies.

What Are The Main API Functions In Node.js?

Asynchronous or non-blocking: a function to control operations to increase playback speed dramatically. Thanks to the non-blocking process, the programmer can perform several operations simultaneously without waiting for the server's response at each stage, increasing the speed.

Synchronous or Blocking: This feature allows threads to be queued. It creates a sequential operation one after the other for a multithreaded structure. We advise against using this feature for single-threaded tasks.

What Is The Difference Between Asynchronous And Non-Blocking Modes?

The asynchronous mode is when we do not receive a response immediately. There is no dependence on the execution of the action. The server stores information and will accept confirmation only when an action is performed. We use this mode to improve efficiency and productivity in general.

The non-blocking mode does not stop or block any operations. In contrast to the asynchronous mode, we will receive the response immediately. If there is no data, then there will be an execution error.

Callback Hell: Identify, Describe, Solve

It is better to start with callback identification. In short, it is a function that takes some time to produce a result. Callback hell is usually caused by coding with complex nested callbacks when each callback takes an argument resulting from the previous callbacks. Thus, you get a code that looks like a pyramid: it takes time to read and understand since it is too difficult.

There is no simple way to solve it, but you can avoid a callback hell by using an event queue.

Middle: Node.js Technical Interview Questions

They say that developers cannot have an average level because they are either a beginner or already experienced. But as practice shows, experience in specific technologies can be obtained unevenly or only in already familiar functions or projects. Developers who are constantly studying Node.js say that the most challenging thing is to understand for yourself what level you already belong to because there are still several issues ahead to be solved with technology.

That's why here, too, they often focus on years: two-three years is already allowed to say a 'middle developer.' The primary categories and Node.js interview questions for experienced professionals may be the same as those for beginners, but the answers should be more in-depth, with examples. It is best to check with a technical test or offer to solve a genuine case (for which you already have a solution). Still, an interview will also be helpful because it allows you to explore the logic of thinking and the ability to find answers and develop something new.

What Is REPL In Node.js?

In the context of Node.js, REPL means read, evaluate, print and loop. The Node REPL is a computing environment in which any command entered is met with a system's response. The REPL environment performs the following tasks by default:

  • Read: Reads the input and converts it to a JavaScript data structure, storing it in memory
  • Eval: It gets the data structure and evaluates it 
  • Print: gives the result
  • Loop: Repeat the given command until CTRL + C before you press it twice.

What disadvantages do you see in using Node.js?

The question indirectly touches on some other technologies, such as C# and Java, for example. Besides, it covers some obsolete types of Node.js usage, such as relational databases. It is about responsiveness under intensive CPU computation. When you hire senior Node.js developers, candidates should see in what applications the effectiveness of Node.js is questionable and why this technology is not a silver bullet in each case.

However, when you hire senior Node.js developers as experts, they can already clearly name the following points and explain what solutions they propose to use:

Unstable API is due to frequent updates and a lack of backward compatibility. An experienced developer knows to change the code with a new version constantly.

Asynchrony sometimes causes callback nightmares and degrades the app's performance. It is vital to avoid a situation where callbacks are nested several levels deep within other callbacks, making the JavaScript code challenging to maintain.

Node.js doesn’t provide a full-fledged toolkit, so developers are forced to add additional libraries.

Name A Few Common Ways To Secure A Node.js Application And Explain How They Work.

There are many ways to enhance the security of the Node application.

Authentication: It helps to protect the app from unauthorized access. With Node.js, session-based and token-based methods can be applied to authenticate users.

Validate requests: The app or web page can validate all incoming requests. If the request is inappropriate, incredible, or has an incompatible format, it will be rejected. This also provides additional security.

Additional tools: Third-party tools, like Helmet or Csurf, can be easily integrated to secure Node.js apps. They use different methods that allow picking the best one for specific purposes.

Node.js Security Best Practices

What Are Some Steps To Handle Maintenance Problems In Node?

It is better to start maintenance with the code review because that is where the most critical problems can be hidden. The use of additional tools for auditing is welcome, but it is worth defining the criteria and configuration of microservices. This will help improve code quality and product efficiency. You can also update the technical stack or make appropriate updates to the options.

Senior Node.js Interview Questions

These are more technical Node.js interview questions and answers for experienced developers. Of course, these are complicated questions. Your employee is no longer a beginner but an experienced developer who knows the subtleties and accurately identifies the system's advantages and disadvantages. In this section, not theoretical Node.js expert interview questions but practical issues related to coding and solving complex problems are already critical. With answers to advanced Node.js interview questions, you will have a complete picture of your employee and their appropriate experience for that level.

What is EventEmitter?

A Node.js class has objects that are capable of emitting events. During Node.js interview questions for experienced, the programmer will reply that you can generate events by attaching named events caused by the object using the eventEmitter.on () function. When an object generates attached parts, they will be synchronous.

event emitter node js code example

Why Use WebSocket And Socket.IO for Node.js?

WebSocket is a protocol used to build streaming web applications and real-time communication applications. It enables fast two-way messaging between client and server and deploys real-time applications quickly and efficiently. It works effectively with Node.js, ensuring that real-time communication and data flow are hassle-free. Now you can quickly implement live chat applications with Node.js WebSockets.

What about Socket.IO? It is a JavaScript library based on WebSockets and other technologies. Unlike WebSockets, Socket.IO allows you to send messages to all connected clients. It isn't easy to use proxying and load balancers in WebSockets. Socket.IO supports these technologies out of the box. Socket.IO supports gradual degradation and automatic reconnection when the connection is broken and is easier to use. It may seem like Socket.IO is the best tool for live communication. However, there are several situations where it is better to use WebSockets.

What Are The Streams? How Many Are They?

Node.js interview questions and answers for experienced must be prepared carefully. Developers know that threads process files sequentially without relying on memory. However, there are cases when the JS file size is larger than the memory. Solving the Node.js interview questions for experienced, the programmer will answer you on what to do. There is only one way out – using streams to read the file in bits and save space in memory. Streams are like communication channels that read data from the source and sequentially transmit it to the destination. Streams are very efficient when dealing with enormous amounts of data.

There are four types of streams in Node.js, which are:

  • Readable: Used to read large amount of data from source - fs.createReadStream()
  • Writeable: Used to write data to destination - fs.createWriteStream()
  • Duplex: Used for both read and write -net. Socket
  • Transform: A duplex stream used for data modification - zlib.createDeflate()

Streams allow Node.js to work with streaming data in, for example, live video streaming, like Instagram LIVE or Twitch. By the way, do you know how to make a video streaming website with great profit?

How To Improve The Performance Of Node.js Through Clustering?

One of the critical advanced Node.js interview questions that you should ask. Node.js applications run on a single processor. What does it mean? They will not use multi-core systems by default. We use clustering to run multiple processes by instantiating an event loop. When we start using the cluster in a Node.js application behind the scenes, numerous Node.js processes are created. However, there is also a parent process called the cluster manager. It is responsible for monitoring the state of individual instances of your web application.

node js cluster manager

What Is Tracing?

This Node module enables you to use trace events, tracking information generated by V8, user-space code, and Node.js core on the central system. Answering advanced Node.js interview questions, the specialist will tell that the first task is to define the Node app pattern and perform system data monitoring. Tracing will give you an idea of performance and help troubleshoot future memory problems.

What Are The Functions Of Middleware?

Middleware functions are needed to req (change request objects) and res (response objects). It creates a req-res loop. The parts work by providing access to req and res. Besides req and res, there is one more parameter: the following function -next (), which ensures that the request does not hang and time out.

What Is Libuv, And How Does It Work?

It is a multi-platform C library supporting asynchronous I / O-based operations such as file systems, networking, and concurrency. The LibUV library processes the thread pool in Node.js.

modules dependent on libuv

What Are Child Processes? What Is The Difference Between Spawn And Fork?

Being single-threaded but scalable, Node.js allows developers to take advantage of multiple processes. Thus, a large workload is quite acceptable. When you hire senior Node.js developers, they can create and handle child processes in Node.js using the child process module.

These processes interact, which is why Node.js got its codename: node-to-node communication. How to create child processes? You can use Spawn () to execute system commands. Its peculiarity is that once it is launched, it does not execute additional code in the process. If you have a command inside another command, the fork () method is acceptable, which will start a new instance of the V8 engine.

How To Prepare for Node.js Interview – AnyforSoft Advice

As a company with ten years of international experience, AnyforSoft knows that hiring developers for startups could be hard enough. To not miss your person who will be able to create something special in the future, it is essential to follow specific hiring rules. It is crucial to understand which candidate hides the real treasure and which one is not worth wasting your time on. How to prepare for a Node.js interview if you are an employer?

An employer should approach Node.js interview questions and answers for experienced and beginners as straightforwardly as possible. At the first stage of your search for a developer, look at the portfolio of candidates. A candidate who does not show growth and development does not deserve attention. It is essential to prepare in advance Node.js interview coding questions and answers for different levels. We understand that interview questions on Node.js of specialists of different levels differ in complexity.

In interview questions on Node.js, it is also essential to pay attention to how they interact with the team, their values, and their work attitude. The additional questions will help check the software skills of potential employees, their English knowledge, their level of erudition and desire, and their ability to develop. Sometimes Node.js interview specialists with 1-year experience who have a great passion for growth and development are much more valuable than senior Node.js developers who are stuck in place and are focused exclusively on themselves.

When you hire senior Node.js developers or beginners, the main thing is an orientation towards knowledge, human values, and a desire for development. Two aspects that play an essential role in decision-making are technical and personal. If these two puzzles add to a single business values system ​​and requirements, this is an excellent start for collaboration.


It is possible to make hiring Node.js specialists understandable and almost effortless. That is why we have prepared Node.js interview questions and answers for experienced candidates and beginners to make an employer's life much easier. In our article, you can see the questions for the junior, middle, and senior Node.js developers to get acquainted with soft skills questions, which help to get to know the candidate. In this way, you are killing two birds with one stone by asking the right both sides questions.

However, there is another option: to work with a product development team who cares about the result and has the sufficient tech knowledge and deep expertise in the aspects you need. If you are ready to discuss the project, estimate it, or need additional advice, please write to our manager; we are open to collaboration.

Want to work with us?