Read this blog for the top MEAN Stack Interview Questions if you are preparing for an interview for the MEAN Stack Web Developer position.

Digitization is increasingly gaining traction in the modern-day tech industry and many brands and companies are eager to invest in fast, efficient, dynamic applications and websites. MEAN stack offers a quick and organized technique for creating dynamic websites and rapid prototypes for web-based applications. So, learning MEAN Stack development is a great idea to improve your career opportunities in Web Development.

Scope of MEAN Stack Development

Mean Stack is a collection of JavaScript technologies to design and create web applications. Thus, everything is based on JavaScript, from client to server and from server to database. MEAN is a full-stack development toolkit used to develop fast and robust web applications.

MEAN is a user-friendly stack that is the perfect solution for creating dynamic applications and websites. This free and open-source full stack provides a fast and efficient method for making quick prototypes for web-based applications. As most companies and brands depend on websites and applications, MEAN Stack development is one in-demand career choice. 

Top 30 MEAN Stack Developer Interview Questions

We have collated the top 30 MEAN Stack Interview Questions that you should be prepared with if you are serious about a career in MEAN Stack Development. Do go through the following questions before you attend your interview.

Explain the MEAN Stack Architecture

The primary function of the different components of Mean Stack Architecture are as follows:

  • Angular JS: Accepts requests and displays results to the end user
  • NodeJS: Handles client and server requests
  • MongoDB: Stores and retrieves data.
  • Express JS: Make requests to Database and return a response

2. What is the purpose of MongoDB?

MongoDB is a document-oriented database manager created for storing vast volumes of data. It saves data in a binary JSON format and executes the concept of documentation and collection. MongoDB is a NoSQL, cross-platform database integrated with high scalability, high performance, and flexibility that allows for seamless indexing and querying.

3. Explain what could be the purpose of ExpressJS?

ExpressJS is a web application framework that supports and hosts Node.js projects. It is an open-source framework that is available within the MIT license. ExpressJS manages the workflow between the database and the frontend and enables a secure and smooth data transfer. It features excellent error handling and web designing functionalities to enhance the web development process.

4. What purpose does AngularJS serve?

AngularJS is a front-end, open-source web application development framework for developing single-page applications maintained by Google. It enables Web Developers to use HTML as their template language and utilize the HTML syntax to represent a web app’s components precisely and clearly.

5. Explain what is a Routing Guard in Angular.

The route guards in Angular are interfaces that tell the router whether or not it should enable navigation to a route that has been requested. Route guards make this decision by looking for a true or false return value from a class that executes the given guard interface. There are five types of guards, each of which is called in a specific sequence. The router’s behavior is altered differently depending on the guard used. The guards are:

  • CanActivate
  • CanActivateChild
  • CanDeactivate
  • CanLoad
  • Resolve

6. Do you think that TypeScript supports all object-oriented principles?

Yes, TypeScript supports all the object-oriented principles. There are four main principles of Object Oriented Programming:

  • Inheritance,
  • Encapsulation,
  • Polymorphism and
  • Abstraction

TypeScript can implement all four object-oriented programming principles with a cleaner and smaller syntax.

7. Explain how the Centralized Workflow works.

The centralized workflow uses a central repository to act as the single point of entry for all modifications to the project. The default development branch is known as master, and all changes are made to this branch. Developers begin by cloning the central repository. They edit files and make changes to their local copies of the project. These new modifications are stored locally. Developers then push their local main branch to the central repository to make changes to the official project. Before a developer can publish their feature, they must fetch the modified central commits and rebase their edits on top of them. The Centralized Workflow has no well-defined forking patterns or pull requests as compared to other workflows.

8. Explain the advantages of using Node.js.

Following are the key advantages of using Node.js

  • Event Driven and Asynchronous - All the APIs of Node.js library are asynchronous, which means non-blocking. It means that a Node.js-based server never waits for an API to return the data. The server goes to the following API after calling it and a notification mechanism of Events of Node.js enables the server to receive a response from the earlier API call.
  • Very Fast – Node.js library is very fast in code execution as it is built on Google Chrome's V8 JavaScript Engine.
  • Single-Threaded but Highly Scalable - Node.js makes use of a single-threaded model with event looping. The event mechanism enables the server to respond in a non-blocking way and makes the server highly scalable compared to traditional servers, which develop limited threads to manage requests. Node.js uses a single-threaded program, and the same program can serve a much larger number of requests than a traditional server such as Apache HTTP Server.
  • No Buffering - Node.js applications never buffer any data. These applications output the data in chunks.

9. Explain what Containerization means.

Containerisation is a kind of virtualization strategy that came as a substitute for traditional hypervisor-based virtualization. The different containers share the operating system in containerization instead of being cloned for each virtual machine. For example, Docker offers a container virtualization platform that is an excellent alternative to hypervisor-based arrangements.

10. Explain the scenarios when Node.js should not be used.

Node.js can be used for spreading applications. In cases where the system requires a long interval, we should not use Node.js. If the server performs some calculations, then it may not be able to method the other requests at that time. Thus, if there is a method that requires a less dedicated C.P.U. time, then Node.js is a perfect choice.

Node.js should be used for applications that require a long processing time. This is because a single-threaded node is organized. Therefore, if a single application requires long-running calculations in the background, it cannot process further requests.

11. Explain what Data Modeling is.

In the MongoDB and Mongoose context, data modeling controls what data can be present in a database and what data should be in a document. You may want to be able to save the email address, last name, first name, and telephone number while keeping the user information. But you only require an email address and the first name, and the email address needs to be unique. This information is the basis for the data model in a schema.

12. Explain callback in Node.js.

The callback function in Node.js is used to address various server requests. For example, if you have a massive file that a server will take time to read and you do not want a server to read that big file, then the callback function is used once the other requests are addressed. Call back enables the server first to manage the pending request and to call a function after completing the request.

For example, suppose there is a file read function. In that case, Node.js automatically sends the control to the execution environment after it begins reading the file for the next instruction to be executed. Once the read operation of the file is completed, the callback function is called and then the file’s content is passed as its argument. This feature makes Node.js very scalable. Many queries are processed without waiting for any feature to return the expected result.

13. What is the usage of a buffer class in Node.js?

The buffer class in Node.js is used to store raw data as an entire array. However, it is similar to a primitive memory assignment available outside the V8 heap. It is a global class that can be accessed easily without importing a buffer module in an application. Buffer classes are used as pure JavaScript is not compatible with binary data. Thus, handling octet streams while dealing with TCP streams or the file system is important.

14. Explain why we use mean stack.

Web applications can easily be created with Node.js as they provide a good number of JavaScript modules from their enormous library. Mean stack allows developers to write JavaScript code only in one language, which is a quick and simple language on both the server and the client pages.

15. Explain the Event Emitter of Node.js.

You can design and handle customized events with an event module available in Node. Js. You must note that the event module comprises the game emitter class, that can be used for managing and raising personalized events. Furthermore, you must also note that when an event emitter identifies an error, emits an error case. On the other side, it also sends a sample with the new user’s name if a new user is added. Also, it sends a demonstration by the remote user’s name once the current user is disabled.

16. What is REPL In Node.Js?

Read Eval Print Loop or REPL is a simple program that accepts and evaluates commands and then prints the results. REPL creates an environment identical to a Linux/Unix shell or a Windows console, wherein you can specify system and command and respond with the output. Following are the functions performed by the REPL:

  • READ – Reads the input offered by the user, parses it into JavaScript data structure, and then stores it in the memory.
  • EVAL – Runs the data structure.
  • PRINT – Prints the outcome generated once the command is evaluated.
  • LOOP – Loops the above command until the user presses Ctrl+C twice.

17. Describe Scope in JavaScript.

Each function has a scope in JavaScript, which is basically a group of rules and variables describing how their unique name can access those variables. You can access a function’s scoped variables only via the code available inside that function. However, variables present in a particular scope must have unique names and scope can exist within another scope. In such a scenario, the code of the innermost scope can access the variables available in either of the scopes.

18. Define Dependency Injection.

Dependency Injection is a software design concept that enables you to inject or use a service in ways that are not dependent on any client consumption. By doing so, you fundamentally stop the client from making modifications to the dependencies once the underlying service changes. The main purpose of dependency injection is to segregate the creation of clients’ dependencies from their behavior, thus letting you design loosely coupled programs.

19. What purpose do Indexes serve in MongoDB?

In MongoDB, indexes facilitate and support efficient query execution. Without indexes, MongoDB has to execute a collection scan wherein it needs to scan each document in a collection and choose the suitable documents matching the query statement. However, if an appropriate index has been assigned to each query, MongoDB can utilize the index to restrict the number of documents it has to evaluate.

20. Define “Decorators” in TypeScript.

In TypeScript, a Decorator indicates a special kind of declaration that is usually associated with a class declaration, accessor, method, property, or parameter. Decorators are functions that consider their target as an argument. They enable you to execute arbitrary code about the target execution or even swap the target with a new definition altogether.

21. Define Cross-site Scripting (XSS).

Cross-site Scripting (XSS) is a client-side code injection attack, where malicious scripts are run in the web browser by integrating malicious code in a genuine web application or web page. It can also happen when you click on suspicious links that can pass private information and cookies to attackers. The attack happens once you visit a web app or a web page that executes malicious code. Thus, the web app or the web page turns into a vehicle to transport malicious scripts to the browser of a user.

22. Define AOT and mention its benefits.

Angular applications comprise HTML templates along with the standard components. As the browser cannot understand these components and HTML templates directly, Angular apps must first be compiled before you can execute them in a browser. The Angular ahead-of-time (AOT) compiler changes the TypeScript code and Angular HTML into JavaScript code during the build phase before the browser downloads and executes the code. Compiling the Angular application in the build stage boosts a faster launch of Angular apps in the browser. 

Following are the benefits of using AOT:

  • The browser can download a pre-compiled version of the application. The browser downloads executable code to render the Angular application immediately, without waiting for the app to compile first.
  • The compiler inlines the CSS style sheets and external HTML templates within the application JavaScript with AOT, thus, removing separate AJAX requests for source files.
  • The AOT compiler detects and reports any template binding errors during the build stage.
  • Since AOT compiled HTML components and templates into JavaScript files before serving them as clients, there are no more templates left to read and no more risky client-side HTML/JavaScript evaluation requirements. This decreases the possibility of any injection attacks.

23. What is a Grid System in CSS?

A grid system is a structure used for stacking content both horizontally and vertically in a reliable and efficient manner. Grid systems have two core components – columns and rows. Some of the most used grid systems include Pure, Simple, Bootstrap, Flexbox, and Foundation.

24. Explain what is a Service and when you use it.

Angular services are singleton objects that get instantiated once during the lifetime of an application. They comprise methods that handle and maintain data through the life of an application, that is the data is not refreshed and is available all the time. The main aim of a service is to share and organize models, business logic, or data and functions with various components of an Angular application.

25. Explain the difference between classes and cases in Typescript

Classes are used as object factories. A class describes a blueprint of what an object should appear and act like and then implements that blueprint by defining methods and initializing class properties. Classes are present through all the phases of our code.

An interface is a virtual structure that is only present within the context of TypeScript. Interfaces are used by a TypeScript compiler only for type-checking purposes. Once the code is converted to its target language, it is removed from interfaces.

26. Are you aware of the top DevOps tools?

The most popular DevOps tools are:

  • Jenkins: Continuous Integration tool
  • Docker: Containerization tool
  • Git: Version Control System tool
  • Puppet, Chef, Ansible: Configuration Management and Deployment tools
  • Selenium: Continuous Testing tool
  • Nagios: Continuous Monitoring tool

27. Could you explain the difference between ES5 and ES6

  • ECMAScript 5 (ES5): It is the 5th edition of ECMAScript, which was standardized in 2009. This standard has been implemented pretty much in all modern browsers
  • ECMAScript 6 (ES6)/ ECMAScript 2015 (ES2015): It is the 6th edition of ECMAScript, which was standardized in 2015. This standard has been partially implemented in most modern browsers.

28. Explain the main difference between REST and GraphQL

The key difference between GraphQL and REST is that GraphQL does not have devoted resources, but everything is considered as a graph and therefore is linked and can be queried to an app’s exact needs.

29. How is TypeScript an optionally statically typed language?

TypeScript is referred to as optionally statically typed, which means that you can tell the compiler to disregard the type of a variable. Using the data type, we can allocate any type of value to the variable. TypeScript does not display any error for checking during compilation.

30. How does Node.js handle Child Threads?

Node.js, fundamentally, is a single thread process. It does not display thread management methods and child thread to the developer. .Js does display child threads for certain tasks such as asynchronous I/O, but these are executed behind the scenes and do not run any application JavaScript code, nor block the main event loop. If threading support is required in a Node.js application, then there are tools available to enable it, for example, the ChildProcess module.


This blog has provided you with the top commonly asked MEAN Stack Interview Questions. Make sure you go through all the questions and answers provided in this article. 

We suggest the Post Graduate Program in Full Stack Web Development from SimpliLearn for excellent web developer programs. This program can help you chart your career towards being a MEAN stack developer. The program will help you learn skills such as Express.js, MongoDB, Angular, and Node.js (“MEAN”), along with GIT, HTML, CSS, and JavaScript to build and deploy interactive applications and services throughout this program.

Also, if cloud solutions interest you, then we suggest the AWS Cloud Architect program from SimpliLearn. This AWS Cloud Architect Certification Course will help you with the expertise and knowledge you require in Amazon Web Services (AWS).

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