Node.js Interview Questions: Beginner to Advanced (With Answers)

Node.js Interview Questions and Answers For Freshers

Start with the fundamentals: core Node.js concepts, basic modules, and how asynchronous JavaScript works. These interview questions in Node.js help you build a strong base before moving to Express, APIs, and real-world use cases.

1. What is Node.js, and where can you use it?

Node.js is an open-source, cross-platform JavaScript runtime environment and library to run web applications outside the client’s browser. It is used to create server-side web applications.

Node.js is perfect for data-intensive applications as it uses an asynchronous, event-driven model. You can use  I/O-intensive web applications, such as video streaming sites. You can also use it to develop real-time web applications, Network applications, General-purpose applications, and distributed systems.

2. Why use Node.js?

Node.js makes it easy to build scalable network programs. Some of its advantages include:

• It is generally fast
• It rarely blocks
• It offers a unified programming language and data type
• Everything is asynchronous 
• It yields great concurrency

3. How does Node.js work?

Node.js uses an event-driven, non-blocking I/O approach to handle work efficiently. When a request comes in, the event loop handles it. If something time-consuming comes up, such as reading a file or running cryptographic operations, that task is sent to a background thread managed by libuv.

Once it’s done, the result is pushed back to the queue and processed without stopping the main thread. Because of this setup, Node.js can handle a large number of requests simultaneously without slowing down.

4. Why is Node.js single-threaded?

Node.js uses a single main thread to execute JavaScript, keeping execution predictable and lightweight. However, it is not limited to one thread overall.

Heavy tasks such as file I/O, DNS lookups, and cryptographic operations are handled by background threads via libuv, and CPU-intensive work can be offloaded using worker threads when needed.

5. If Node.js is single-threaded, then how does it handle concurrency?

Node.js handles concurrency using the event loop and async APIs. Rather than spinning up a new thread for each request, it registers callbacks or promises and moves on to other work.

When an async task finishes, the event loop picks it up and processes the result. That’s how Node.js can deal with thousands of connections at the same time without falling over.

6. Explain callback in Node.js.

A callback function is called after a given task. It allows other code to be run in the meantime and prevents any blocking.  Being an asynchronous platform, Node.js heavily relies on callback. All APIs of Node are written to support callbacks.

7. What are the advantages of using promises instead of callbacks?

• Promises provide a cleaner and more structured way to handle asynchronous operations
• They avoid deeply nested callbacks, make error handling more predictable using .catch(), and work seamlessly with async/await syntax
• Promises improve readability, debugging, and maintainability in modern Node.js applications

8. How would you define the term I/O? 

• The term I/O is used to describe any program, operation, or device that transfers data to or from a medium and to or from another medium
• Every transfer is an output from one medium and an input into another. The medium can be a physical device, network, or files within a system

9. How is Node.js most frequently used?

Node.js is widely used in the following applications:

1. Real-time chats
2. Internet of Things
3. Complex SPAs (Single-Page Applications)
4. Real-time collaboration tools
5. Streaming applications
6. Microservices architecture

11. What is NPM?

NPM stands for Node Package Manager, which manages all packages and modules for Node.js.

Node Package Manager provides two main functionalities:

• Provides online repositories for Node.js packages/modules, which are searchable on search.nodejs.org
• Provides a command-line utility to install Node.js packages and also manages Node.js versions and dependencies

12. What are the modules in Node.js?

Modules are like JavaScript libraries that can be used in a Node.js application to include a set of functions. To include a module in a Node.js application, use the require() function with the parentheses containing the module's name.

Node.js has many modules to provide the basic functionality needed for a web application. Some of them include:

13. What is the purpose of the module.exports?

In Node.js, a module encapsulates related code into a single unit that can be parsed by moving all relevant functions into a single file. You may export a module and its function, allowing it to be imported into another file with the needed keyword.

14. Why is Node.js preferred over other backend technologies like Java and PHP?

Node.js works well when you need to handle many requests without waiting on slow I/O. Its non-blocking model helps with that. Another plus is that you can use JavaScript on both the client and the server, which keeps things simple.

The npm ecosystem also makes it easy to pull in libraries and tools. That said, Node.js isn’t the best choice for everything. For heavy CPU work, languages like Java or PHP can still be a better fit.

15. What is the difference between Angular and Node.js?

Node.js has a solid presence on the web. According to W3Techs, Node.js is used by around 5.7% of all websites with a known web server technology, indicating steady adoption in production environments.

16. Which database is more popularly used with Node.js?

MongoDB is the most common database used with Node.js. It is a NoSQL, cross-platform, document-oriented database that provides high performance, high availability, and easy scalability.

17. What are some of the most commonly used libraries in Node.js?

There are two commonly used libraries in Node.js:

• ExpressJS - Express is a flexible Node.js web application framework that provides a wide set of features to develop web and mobile applications.
• Mongoose - Mongoose is also a Node.js web application framework that makes connecting an application to a database easy.

18. What are the pros and cons of Node.js?

Node.js offers fast execution, excellent scalability, and strong support for real-time applications. It uses JavaScript, which simplifies full-stack development, and has a mature ecosystem via npm.

On the downside, Node.js is not ideal for CPU-heavy tasks unless worker threads are used, and poorly written asynchronous code can still become hard to maintain.

19. What is the command used to import external libraries?

The “require” command is used for importing external libraries. For example - “var http=require (“HTTP”).”  This will load the HTTP library and the single exported object through the HTTP variable.

20. What are common security vulnerabilities in Node.js applications?

Node.js apps can face security issues, especially when handling user input, authentication, or API access. Most of these problems come from weak input checks, unsafe settings, or dependencies that haven’t been updated in a while.

Some of the most common security issues include:

• Cross-site scripting (XSS)
• Cross-site request forgery (CSRF)
• SQL or NoSQL injection attacks
• Insecure JWT handling
• Improper CORS configuration

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21. What does event-driven programming mean?

An event-driven programming approach uses events to trigger various functions. An event can be anything, such as typing a key or clicking a mouse button. A call-back function is already registered with the element executes whenever an event is triggered.

22. What is an Event Loop in Node.js?

Event loops handle asynchronous callbacks in Node.js. It is the foundation of Node.js's non-blocking input/output in Node.js, making it one of the most important environmental features.

23. Differentiate between process.nextTick() and setImmediate()?

process.nextTick() schedules a callback to run immediately after the current operation completes, before the event loop continues. setImmediate() schedules a callback to execute in the check phase of the next event loop iteration.

Overusing process.nextTick() can block the event loop, while setImmediate() is safer for deferring execution.

24. What is an EventEmitter in Node.js?

• EventEmitter is a class that holds all the objects that can emit events
• Whenever an object from the EventEmitter class throws an event, all attached functions are called upon synchronously

25. What are the two types of API functions in Node.js?

The two types of API functions in Node.js are:

• Asynchronous, non-blocking functions
• Synchronous, blocking functions

26. What is the package.json file?

The package.json file is the heart of a Node.js system. This file holds the metadata for a particular project. The package.json file is found in the root directory of any Node application or module.

This is what a package.json file looks like immediately after creating a Node.js project using the command: npm init

You can edit the parameters when you create a Node.js project.

27. How would you use a URL module in Node.js?

The URL module in Node.js provides various utilities for URL resolution and parsing. It is a built-in module that helps split up the web address into a readable format.

28. What is the Express.js package?

Express is a flexible Node.js web application framework that provides a wide set of features to develop both web and mobile applications.

29. How do you create a simple Express.js application?

• The request object represents the HTTP request and has properties for the request query string, parameters, body, HTTP headers, and so on
• The response object represents the HTTP response that an Express app sends when it receives an HTTP request

30. What are streams in Node.js?

Streams are objects that enable you to read data or write data continuously. There are four types of streams:

• Readable: Used for reading operations
• Writable: Used for write operations
• Duplex: Can be used for both read and write operations
• Transform: A type of duplex stream where the output is computed based on the input

31. How do you create a simple server in Node.js that returns Hello World?

• Import the HTTP module
• Use createServer function with a callback function using request and response as parameters
• Type “hello world." 
• Set the server to listen to port 8080 and assign an IP address

32. Explain asynchronous and non-blocking APIs in Node.js.

• All Node.js library APIs are asynchronous, which means they are also non-blocking
• A Node.js-based server never waits for an API to return data. Instead, it moves to the next API after calling it, and a notification mechanism from a Node.js event responds to the server for the previous API call

33. How do we implement async in Node.js?

The async code asks the JavaScript engine running the code to wait for the request.get() function to complete before moving on to the next line for execution.

34. What is a callback function in Node.js?

A callback is a function called after a given task. This prevents any blocking and enables other code to run in the meantime.

35. What is CORS, and why is it important in Node.js APIs?

CORS stands for Cross-Origin Resource Sharing. It controls which websites can access your API. Without proper CORS settings, your API could be accessed by unwanted or malicious origins.

In production environments, CORS should never be left open to all origins. Instead, it should be carefully restricted to trusted domains. This helps prevent unauthorized access and improves overall application security.

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36. What is REPL in Node.js?

REPL stands for Read-Eval-Print-Loop, representing a computer environment. It’s similar to a Windows console or a Unix/Linux shell, where a command is entered. Then, the system responds with an output

37. What is the control flow function?

The control flow function is a code that runs between several asynchronous function calls.

38. What is the difference between fork() and spawn() methods in Node.js?

fork()	spawn()
fork() is a particular case of spawn() that generates a new instance of a V8 engine.	Spawn() launches a new process with the available set of commands.
Multiple workers run on a single node code base for multiple tasks.	This method doesn’t generate a new V8 instance, and only a single copy of the node module is active on the processor.

39. What is the buffer class in Node.js?

The Buffer class stores raw data similar to an array of integers, but corresponds to a raw memory allocation outside the V8 heap. The Buffer class is used because pure JavaScript is not compatible with binary data.

40. What is piping in Node.js?

Piping is a mechanism for connecting the output of one stream to the input of another. It is normally used to retrieve data from one stream and pass output to another stream

41. What is a memory leak in a Node.js application, and how can you detect it?

A memory leak happens when a Node.js application keeps using memory that it no longer needs. Over time, this unused memory keeps growing, which can slow down the application or even cause it to crash. Memory leaks are more serious in Node.js because applications often run for long periods without restarting.

To understand whether a memory leak exists, developers usually start by observing memory usage patterns over time. If memory keeps increasing even when the workload remains the same, it is a strong sign of a leak. Developers then rely on profiling tools to investigate further.

Some common ways to detect memory leaks include:

• Monitoring memory usage using process.memoryUsage()
• Taking heap snapshots and comparing them to see which objects are growing
• Using profiling tools to track retained objects and references

42. How do you fix memory leaks once they are identified?

Once a memory leak is found, the next step is to understand what is holding onto the memory. In many cases, the issue comes from references that are never released.

To fix memory leaks, developers usually focus on a few practical habits that make a real difference:

• Remove event listeners, timers, or intervals that are no longer needed
• Avoid keeping data in global variables unless it’s truly required
• Keep in-memory caches small and clear them when possible
• Ensure closures don’t retain references longer than necessary
• Use streams for large data instead of loading everything into memory at once

43. What is callback hell?

• Callback hell, also known as the pyramid of doom, is the result of intensively nested, unreadable, and unmanageable callbacks, which in turn makes the code harder to read and debug
• improper implementation of the asynchronous logic causes callback hell

44. What is a reactor pattern in Node.js?

A reactor pattern is a design pattern for non-blocking I/O operations. This pattern provides a handler for each I/O operation. As soon as an I/O request is generated, it is then submitted to a demultiplexer.

45. How do you securely handle JWT authentication in Node.js?

JWTs are commonly used for authentication in Node.js applications, but they must be handled carefully. A JWT is only safe if it is properly signed, stored, and validated.

To secure JWT authentication, developers usually follow a few best practices:

• Use strong secrets or private keys for signing tokens
• Set expiration times to prevent long-lived tokens
• Avoid storing sensitive data inside the token payload
• Prefer HttpOnly cookies when security is critical
• Always validate the token before trusting it

46. For Node.js, why does Google use the V8 engine?

Node.js is built on Google’s V8 engine. V8 uses Just-In-Time compilation to turn JavaScript into machine code, so things run fast. Memory handling is also efficient, which helps with performance. Since V8 behaves consistently across platforms, Node.js works well for large server-side applications.

47. How do you protect a Node.js application from CSRF attacks?

CSRF attacks happen when a user is tricked into doing something they didn’t mean to, like submitting a form or clicking a link. Apps that use cookies for authentication are usually the ones most at risk.

To protect against CSRF, developers usually combine multiple strategies:

• Using CSRF tokens to verify requests
• Setting cookie attributes like SameSite
• Avoiding unsafe HTTP methods for sensitive actions
• Using authorization headers instead of cookies where possible

48. Explain the concept of middleware in Node.js.

Middleware is a function that receives the request and response objects. Most tasks that the middleware functions perform are:  

• Execute any code
• Update or modify the request and the response objects
• Finish the request-response cycle
• Invoke the next middleware in the stack

49. What are the different types of HTTP requests?

HTTP defines a set of request methods for performing desired actions. The request methods include:

• GET: Used to retrieve the data
• POST: Generally used to make a change in state or reactions on the server
• HEAD: Similar to the GET method, but asks for the response without the response body
• DELETE: Used to delete the predetermined resource

50. How would you connect a MongoDB database to Node.js?

To create a database in MongoDB:

• Start by creating a MongoClient object
• Specify a connection URL with the correct IP address and the name of the database you want to create

Developer usage remains strong as well. The Stack Overflow Developer Survey reports that 40.8% of developers actively use Node.js, and 64.2% of those developers want to continue using it, highlighting high long-term confidence in the technology.

51. What testing tools are commonly used in Node.js projects?

Testing is an essential part of Node.js development. It helps ensure that applications behave correctly and remain stable as they grow.

Most Node.js projects rely on tools like Jest for unit and integration testing. Jest provides assertions, mocking, and test runners in a single package. For API testing, Supertest is commonly used to simulate HTTP requests and verify responses.

52. How do you test an API endpoint in Node.js?

When testing an API endpoint, developers usually start small, checking the logic piece by piece. Then they test the full request and response to make sure everything works as expected.

The typical testing process includes:

• Writing unit tests for business logic
• Using Supertest to test HTTP routes
• Mocking databases or external services
• Verifying both successful responses and error cases

53. What is the difference between unit testing and integration testing?

Unit testing is about testing small pieces of your code, such as individual functions or modules. These tests run fast and help catch logic mistakes early.

Integration testing looks at how different parts of your app work together, including routes, middleware, and databases. Both types of testing are useful for keeping Node.js applications reliable.

54. How would you design a scalable Node.js API?

Scalability is a key concern in system design interviews. A scalable Node.js API should handle increasing traffic without performance issues.

To achieve scalability, developers usually design APIs that are:

• Stateless, so any server can handle requests
• Load-balanced across multiple instances
• Optimized with caching mechanisms
• Protected with rate limiting
• Designed to fail gracefully

55. How do you ensure high availability in Node.js systems?

In production, things break all the time. High availability is about designing the system so it keeps running anyway, without users feeling the impact.

Teams usually improve availability by doing a few key things:

• Using load balancers
• Monitoring service health
• Isolating failures using microservices
• Using message queues for asynchronous tasks

56. Why is logging important in Node.js applications?

Logging helps developers understand what is happening inside an application, especially in production. Without logs, debugging issues becomes very difficult.

Most Node.js applications use structured logging tools that record logs with timestamps and severity levels. These logs are often collected in centralized systems for easy analysis and alerting.

57. How do you monitor a Node.js application in production?

Monitoring is about keeping an eye on how an application behaves in real use. Teams usually monitor metrics such as response time, error rates, CPU load, and memory usage.

When these numbers start to look off, monitoring tools surface the issue and send alerts. That gives developers a chance to step in and fix problems before users notice anything.

58. What are the best practices for structuring a Node.js project?

A well-structured project is easier to maintain and scale. Features rather than file types usually organize Node.js projects.

A good project structure includes:

• Separating routes, controllers, and services
• Using environment variables for configuration
• Centralized error handling
• Keeping business logic separate from server setup

59. How should environment configuration be handled securely?

Configuration often includes sensitive data such as API keys and database credentials. These should never be hardcoded.

Developers handle configuration securely by:

• Using environment variables
• Keeping secrets out of version control
• Using secret management tools in production
• Maintaining separate configs for different environments

60. What is WASI, and why is it being introduced?

The WASI class implements the WASI API and provides additional convenience methods for interacting with WASI-based applications. Every WASI instance represents a unique sandbox environment.

Each WASI instance must specify its command-line parameters, environment variables, and sandbox directory structure for security reasons.

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61. What is a first-class function in Javascript?

First-class functions are a powerful feature of JavaScript that allows you to write more flexible and reusable code. In Node.js, first-class functions are used extensively in asynchronous programming to write non-blocking code.

62. How do you manage packages in your Node.js project?

Managing packages in your Node.js project is done with the Node Package Manager (NPM), which lets you install and manage third-party packages and create and publish your own.

63. How is Node.js better than other frameworks?

Node.js is a server-side JavaScript runtime environment built on top of the V8 JavaScript engine, the same engine that powers Google Chrome. It makes Node.js very fast and efficient, as well as highly scalable.

64. What is a fork in Node.js?

The Fork method in Node.js creates a new child process that runs a separate Node.js instance and can be useful for running CPU-intensive tasks or for creating a Node.js server cluster.

65. List down the two arguments that async. First, does the queue take as input?

The async.queue function in Node.js takes two arguments: a worker function and an optional concurrency limit. It is used to create a task queue executed in parallel.

66. What is the purpose of the module.exports?

The module. The exports object in Node.js is used to export functions, objects, or values from a module and is returned by the require() function when another module requires it.

67. What is the difference between JavaScript and Node.js?

Node.js is a runtime environment for executing JavaScript code outside of a web browser, while JavaScript is a programming language that can be executed in both web browsers and Node.js environments.

68. What are the asynchronous tasks that should occur in an event loop?

Asynchronous tasks that should occur in an event loop in Node.js include I/O operations, timers, and callback functions. By performing these tasks asynchronously, Node.js can handle a large number of concurrent requests without blocking the event loop.

69. What is the order of execution in control flow statements?

In Node.js, control flow statements are executed in a specific order. The event loop determines the execution order. The event loop is a mechanism in Node.js that allows non-blocking I/O operations to be executed.

70. What are the input arguments for an asynchronous queue?

An asynchronous queue in Node.js is a data structure that allows functions to be executed in a specific order. Functions are added to the queue and are executed in the order that they were added. An asynchronous queue is useful when executing a series of functions in a specific order.

71. Are there any disadvantages to using Node.js?

Node.js is less suitable for CPU-intensive tasks due to its single-threaded JavaScript execution model, though worker threads can help. Poorly managed asynchronous code can also lead to complexity. However, memory usage depends on the application's design rather than on Node.js itself.

72. What is the primary reason for using the event-based model in Node.js?

The main reason to use the event-based model in Node.js is performance. The event-based model allows non-blocking I/O, enabling Node.js to handle a large number of connections without consuming much resources.

73. What is the difference between Node.js and Ajax?

Ajax and Node.js are two different technologies that are used for different purposes. Ajax is a client-side technology allowing asynchronous communication between the client and the server. It is typically used to update parts of a web page without requiring a full page reload. 

Node.js, on the other hand, Node.js is a server-side technology used for building fast, scalable, and efficient server-side applications. It is typically used for real-time applications like chat, online games, and streaming services.

74. Why is Node.js quickly gaining attention from JAVA programmers?

Node.js is quickly gaining attention from Java programmers because it is fast, scalable, and efficient. Java is a popular server-side technology, but it can be slow and resource-intensive. Node.js, on the other hand, is built on the V8 JavaScript engine, which is known for its speed and performance.

75. What is "non-blocking" in Node.js?

In Node.js, non-blocking refers to the ability of the runtime environment to execute multiple tasks simultaneously without waiting for one task to complete before starting the next. This is achieved through asynchronous I/O, which enables Node.js to handle multiple requests concurrently.

76. How does Node.js overcome the problem of blocking I/O operations?

Node.js uses an event-driven, non-blocking I/O model that allows it to handle I/O operations more efficiently. By using callbacks, Node.js can continue processing other tasks while waiting for I/O operations to complete. This means that Node.js can handle multiple requests simultaneously without causing any delays

Additionally, Node.js uses a single-threaded event loop architecture, which allows it to handle a high volume of requests without any issues.

77. How can we use async await in Node.js?

To use async/await in Node.js, you'll need to use functions that return promises. You can then use the async keyword to mark a function as asynchronous and the await keyword to wait for a promise to resolve before continuing with the rest of the code.

78. Why should you separate the Express app and server?

Firstly, separating your app and server can make it easier to test your code. By separating the two, you can test your app logic independently of the server, making it easier to identify and fix bugs.

Secondly, separating your app and server can make it easier to scale your application. By separating the two, you can run multiple instances of your app on different servers, which can help to distribute the load and improve performance.

Finally, separating your app and server can make switching to a different server easier if necessary. By keeping your app logic separate from your server logic, you can switch to a different server without making any major changes to your code.

79. Explain the concept of stub in Node.js.

In Node.js, a stub is a function that serves as a placeholder for a more complex function. Stubs are typically used in unit testing to replace a real function with a simplified version that returns a predetermined value. Using a stub ensures your unit tests are predictable and consistent.

80. What are the security implementations that are present in Node.js?

One of the most important security features in Node.js is the ability to run code in a restricted environment. This is achieved through a sandboxed environment, which helps prevent malicious code from accessing sensitive data or causing damage to the system.

Another important security feature in Node.js is the use of TLS/SSL to encrypt data in transit. This can help to prevent eavesdropping and ensure that sensitive data is protected.

81. What is Libuv?

Libuv is a critical component of Node.js, enabling I/O operations to be handled in a non-blocking, efficient manner.

82. What are global objects in Node.js?

Global objects in Node.js are objects that are available in all modules without the need for an explicit require statement. Some of the most commonly used global objects in Node.js include process, console, and buffer.

83. What is the use of the connect module in Node.js?

The Connect module can handle various middleware types, such as error-handling, cookie-parsing, and session middleware. Error-handling middleware handles errors that occur during the request/response cycle.

Cookie parsing middleware parses cookies from the request header. Session middleware manages user sessions.

84. What are LTS releases of Node.js?

LTS stands for Long-term support. LTS releases of Node.js are supported for an extended period, usually 30 months from the time of release. These releases are typically more stable and reliable than non-LTS releases and are recommended for production use.

85. What do you understand about ESLint?

ESLint is a popular open-source tool that is used to analyze and flag errors and potential problems in JavaScript code.

86. Define the concept of the test pyramid. Please explain the process for implementing them using HTTP APIs.

The test pyramid is a concept often used in software testing to illustrate the ideal distribution of test types.

The pyramid has three layers: unit tests, integration tests, and end-to-end tests. The idea is that most tests should be at the unit level, with fewer tests at the integration and end-to-end levels.

To implement the test pyramid in terms of HTTP APIs, you can start by writing unit tests for each endpoint in the API. These tests should focus on the endpoint's functionality in isolation, without making any external requests or dependencies

Once the unit tests pass, you can write integration tests that verify the interaction between endpoints and components in the API. Finally, you can write end-to-end tests that test the entire API, from the user interface to the database.

87. What is an Event Emitter in Node.js?

An Event Emitter is a Node.js module that facilitates communication between objects in a Node.js application. It is an instance of the EventEmitter class, which provides methods for listening to and emitting events.

In Node.js, events are a core part of the platform, and they are used to handle asynchronous operations.

88. How to Enhance Node.js Performance through Clustering?

Clustering improves Node.js performance by creating multiple worker processes that share the same server port. Each worker runs on a separate CPU core, allowing better utilization of multi-core systems. Clustering is most effective for stateless applications handling high traffic.

89. What is a thread pool, and which library handles it in Node.js?

A thread pool is a collection of threads that are used to execute tasks in parallel. In Node.js, the thread pool is handled by the libuv library, a multi-platform support library that provides asynchronous I/O.

90. How are worker threads different from clusters?

Worker threads and clusters are two different approaches to leveraging multiple CPUs in Node.js. While clusters create multiple instances of a Node.js process, each running on a separate CPU core, worker threads allow multiple threads within a single process.

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91. How to measure the duration of async operations?

The console.time and console.timeEnd methods allow you to measure the duration of a block of code. The console.time method starts the timer and the console.timeEnd method stops the timer and logs the duration to the console.

The performance.now method provides a more precise way to measure the duration of async operations. It returns the current timestamp in milliseconds, which can be used to calculate the duration of a task.

92. Where is package.json used in Node.js?

The package.json file is located in the root directory of an application and the npm package manager uses it to install and manage the dependencies of an application.

93. What is the difference between readFile and create Read Stream in Node.js?

Create Read Stream is a better option for reading large files, while the read file is a better option for small files. It is important to choose the right method based on the file size and the application's requirements.

94. What is the use of the crypto module in Node.js?

The crypto module is widely used in Node.js applications to generate secure random numbers, create digital signatures, and verify signatures. It also supports various encryption algorithms such as AES, DES, and RSA.

95. What is a passport in Node.js?

Passport is a popular authentication middleware for Node.js. It provides a simple and modular way to implement authentication in Node.js applications.

Passport supports many authentication mechanisms, including username/password, social logins like Facebook and Google, and JSON Web Tokens (JWTs).

96. How to get information about a file in Node.js?

In Node.js, the fs module provides methods for working with the file system. To get information about a file, you can use the fs. stat() method. The fs. stat() method returns an object that contains information about the file, such as the file size, creation date, and modified date.

97. How does the DNS lookup function work in Node.js?

In Node.js, the DNS module provides methods for performing DNS lookups. DNS stands for Domain Name System, and it translates domain names into IP addresses. The DNS.lookup () method performs a DNS lookup and resolves a domain name to an IP address.

98. Explain the concept of Punycode in Node.js.

Punycode is a character encoding scheme used in the Domain Name System (DNS) to represent Unicode characters with ASCII characters. It encodes domain names that contain non-ASCII characters, such as Chinese or Arabic characters.

99. What are the Challenges with Node.js?

Challenges with Node.js include handling CPU-intensive workloads, managing complex asynchronous flows, and ensuring proper error handling. Choosing the right architecture and using tools like worker threads and proper monitoring can address most of these challenges.

100. Why do you think you are the right fit for this Node.js role?

I’ve built and scaled backend services with Node.js, with a solid grasp of async code, APIs, and performance tuning. I’m used to working with teams, adjusting to changing project needs, and shipping features that actually run in production.

A highly engaged Reddit discussion titled “Node JS - What is the roadmap in 2026?” shares practical experiences from developers actively working with Node.js.

Many redditors say that while Node.js remains relevant, interviews now focus more on real-world problem-solving, async behavior, and backend design rather than just theory.

Key Takeaways

• Interview questions in Node.js mainly check your clarity of concepts and how well you explain your approach, not just whether the answer is correct
• A solid understanding of the event loop, asynchronous programming, streams, modules, and error handling helps you tackle most Node.js interview questions with confidence
• Practicing Node.js interview questions and answers at beginner, intermediate, and experienced levels prepares you for different interview formats and difficulty levels
• Short, structured Node.js courses and hands-on practice can help you build confidence and prepare in a more organized way

If you want to go beyond quick prep and build job-ready skills in modern web application development, enroll in Simplilearn’s AI-powered Full Stack Developer Program. It strengthens your full-stack foundations and hands-on practice, helping you feel more confident in Node.js interviews.