60 Mern Stack Basic Interview Questions

MERN Stack Basic Interview Questions


  1. Define the MERN Stack and its core technologies.
  2. Explain the advantages and disadvantages of using MERN for web development.
  3. Compare and contrast document and relational databases, highlighting MongoDB’s strengths.
  4. Differentiate between RESTful APIs and traditional web services.
  5. Describe the Single Page Application (SPA) concept and its benefits.
  6. Briefly explain the purpose of npm and package management in MERN.


  1. Differentiate between var, let, and const in JavaScript.
  2. Explain asynchronous code execution and popular methods like Promise and async/await.
  3. Discuss the concept of closures and their practical use cases in JavaScript.
  4. Explain event bubbling and capturing in JavaScript and their impact on event handling.
  5. Explain the difference between props and state in React.js and their impact on component behavior.


  1. List the main data types used in MongoDB and provide examples.
  2. Explain the concept of documents and collections in MongoDB with practical applications.
  3. Differentiate between find, update, and delete operations in MongoDB queries.
  4. Explain the benefits of using sharding in MongoDB and its impact on scalability.
  5. Describe methods for ensuring data security and access control in MongoDB.


  1. Define Express.js and its key features for building web applications.
  2. Explain the concept of middleware in Express.js and its role in application flow.
  3. Describe how routing works in an Express.js application and its different types.
  4. Discuss best practices for error handling in Express.js applications.
  5. Explain techniques for securing an Express.js application against common web attacks.


  1. What is the virtual DOM in React.js and its impact on performance and development?
  2. Differentiate between class-based and functional components in React.js.
  3. Explain the lifecycle methods of a React component and their purpose.
  4. Discuss different methods for managing state in a React.js application.
  5. Describe common performance optimization techniques for React.js applications.


  1. Explain the concept of hooks in React.js and their advantages.
  2. Discuss the role of Redux and other state management libraries in larger MERN projects.
  3. Describe different authentication and authorization methods in MERN applications.
  4. Explain the purpose of testing frameworks like Jest and how to test MERN components.
  5. Discuss deployment strategies for MERN applications on platforms like Heroku or AWS.


  1. Explain how you would debug an unexpected behavior in a running MERN application.
  2. Describe your approach to optimizing the performance of a slow-loading MERN page.
  3. Explain how you would implement user authentication and authorization in a MERN e-commerce website.
  4. Discuss your strategy for handling real-time data updates in a MERN application.
  5. Describe how you would implement a search feature with autocomplete functionality in a MERN web app.


  1. Share your experience with building real-world MERN applications and the challenges you faced.
  2. Explain how you stay up-to-date with the latest advancements in the MERN stack.
  3. Discuss a challenging technical problem you encountered while working with MERN and how you solved it.
  4. Describe your preferred learning resources for staying updated on MERN technologies.
  5. Explain the relationship between the front-end and back-end components of MERN.
  6. Describe the role of APIs in a MERN application and how they interact with the front-end.
  7. Discuss the importance of data validation and security in a MERN application.
  8. Explain the benefits of utilizing a package manager like npm in MERN development.
  9. Compare and contrast different deployment options for a MERN application (e.g., Heroku, AWS).
  10. Briefly explain the purpose of the Express framework in MERN.
  11. Describe different types of routing available in Express and their use cases.
  12. Explain the concept of middleware and its role in handling requests and responses.
  13. Discuss the difference between GET, POST, PUT, and DELETE HTTP methods in the context of APIs.
  14. Briefly explain the purpose of MongoDB in the MERN stack and its data model structure.
  15. Describe your approach to debugging an error encountered in a running MERN application.
  16. Explain how you would implement user registration and login functionality in a MERN application.
  17. Discuss strategies for optimizing the performance of a slow-loading MERN page.
  18. Describe your approach for building a real-time chat feature with MERN.
  19. Explain how you would implement a search engine with filter options in a MERN application.
  20. Describe your learning process for staying updated with the latest advancements in MERN.
  21. Share your experience collaborating with other developers on a MERN project.
  22. Explain your approach to problem-solving and error handling in a Mern environment.
  23. Discuss your preferred workflow for managing and organizing a MERN project.
  24. Describe your experience with testing MERN applications and its importance.


  • Adapt your answers to the specific role and company requirements.
  • Showcase your problem-solving skills and critical thinking ability.
  • Be confident and demonstrate your enthusiasm for the MERN stack.

This is just a starting point, and you can customize these questions to fit your specific needs and interview situation. With thorough preparation and a positive attitude, you can ace your MERN Stack interview!

60 Mern Stack Basic Interview Questions And Answers

1.MERN Stack and its Core Technologies:

MERN Stack refers to a combination of four technologies used to develop web applications:

  • MongoDB: A NoSQL database that stores data in flexible document format, offering scalability and efficient data access.
  • Express.js: A Node.js framework used for building server-side applications, handling routing, middleware, and APIs.
  • React.js: A JavaScript library for building user interfaces with dynamic and interactive components.
  • Node.js: A JavaScript runtime environment that enables server-side JavaScript execution.

2.Advantages of using MERN:

  • Full-stack development: Covers both front-end and back-end with a unified JavaScript language, simplifying development.
  • Scalability and performance: MongoDB and Node.js offer excellent scalability for large datasets and user bases.
  • Rapid development: JavaScript and React’s component-based approach can accelerate development cycles.
  • Large community and resources: Abundant online resources, tutorials, and libraries facilitate learning and troubleshooting.
  • Rich user experiences: React allows for dynamic and engaging user interfaces.

Disadvantages of using MERN:

  • Limited native mobile development: Primarily focused on web development, requiring additional tools for native mobile apps.
  • Learning curve: Requires proficiency in multiple technologies, potentially challenging for beginners.
  • Potential performance bottlenecks: JavaScript can be slower than compiled languages for some scenarios.
  • Security considerations: Managing data security and access control in MongoDB requires careful attention.

3.Document vs. Relational Databases:

Document databases:

  • Store data in flexible JSON-like documents: Easier to model complex data and adapt to changing requirements.
  • No predefined schema: Highly flexible but requires careful data structuring and querying.
  • Scalable and performant: Ideal for large datasets and real-time applications.

Relational databases:

  • Store data in tables with predefined relationships: Easier to enforce data integrity and consistency.
  • Structured and efficient for querying: Excellent for complex data relationships.
  • Limited scalability: Can become cumbersome and less performant for large datasets.

MongoDB’s strengths:

  • Flexible data model: Adapts to evolving data structures without schema changes.
  • Horizontal scalability: Scales easily to handle large data volumes.
  • Efficient for complex data queries: Offers powerful querying capabilities for nested documents and arrays.

4.RESTful APIs vs. Traditional Web Services:


  • Follow REST architectural principles: Consistent and predictable interface for building client-server communication.
  • Resource-oriented: Treat data as resources accessed through standard HTTP methods (GET, POST, PUT, DELETE).
  • Lightweight and flexible: Ideal for building modern web applications and microservices.

Traditional Web Services (SOAP, XML-RPC):

  • Complex protocols and message formats: Can be cumbersome to develop and integrate.
  • Platform-dependent: May require specific languages or frameworks, limiting flexibility.
  • Less widely used in modern web development: RESTful APIs have become the preferred standard.

5.Single Page Applications (SPAs):


  • Dynamic web applications that load a single HTML page: Additional content and data are dynamically loaded and updated without page reloads.
  • Improved user experience: Faster loading times, smoother interactions, and more responsive applications.
  • Complex development and routing: Requires careful attention to state management and user experience.

Benefits of SPAs:

  • Faster loading: Only the necessary content is downloaded, reducing page load times.
  • Smoother interactions: Dynamic content updates without page refreshes, creating a more fluid user experience.
  • Offline functionality: Some SPAs can work offline after initial content is downloaded.

6. npm and Package Management in MERN:

npm: The standard package manager for Node.js applications.

Package management:

  • Manages dependencies: Downloads and installs required libraries and frameworks for MERN development.
  • Keeps versions consistent: Ensures all projects use compatible versions of libraries and dependencies.
  • Simplifies development: Reduces manual configuration and dependency management, saving time and effort.

7. Differentiating var, let, and const in JavaScript:

  • var: Global or function-scoped, can be reassigned, prone to accidental reassignment and scope issues.
  • let: Block-scoped, can be reassigned within its block, prevents accidental global reassignment.
  • const: Block-scoped, cannot be reassigned, enforces data immutability, improves code clarity and security.
  • Asynchronous code: Executes without blocking the main thread, allowing other code to run concurrently.
  • Promise: Represents the eventual completion (or failure) of an asynchronous operation, allowing for chained callbacks.
  • async/await: Syntactic sugar for working with promises, making asynchronous code feel more synchronous.

9.Closures and their practical use cases:

  • Closures: Functions that retain access to the environment of their creation, even after the function itself has returned.
  • Practical use cases: Implementing private variables, currying functions, creating reusable modules, simulating state management.

10.Event bubbling and capturing in JavaScript:

  • Event bubbling: Events propagate up the DOM tree, reaching ancestor elements after targeting the child element.
  • Event capturing: Events propagate down the DOM tree, reaching descendant elements before targeting the child element.
  • Impact on event handling: Used to capture events before they reach their target, or to handle them at different levels of the DOM hierarchy.

11. Props vs. state in React.js:

  • Props: Data passed down from parent to child components, immutable, used for configuring and rendering the child component.
  • State: Internal data managed by a component, mutable, changes trigger re-rendering of the component and its children.
  • Impact on behavior: Props define the initial state and behavior of a component, while state allows the component to dynamically change its behavior based on user interaction or internal logic.

FAQ- 60 Mern Stack Basic Interview Questions

Q1. How do you learn the MERN stack for beginners?

Learn Front-End Languages, Explore Front-End Tools, Get Basics of Website Design,Learn React,Understand MERN Back-End and
Practice Regularly

Q2. Is MERN a tool?

Ans. Developers have a variety of tools to create applications, but a key set gaining prominence in Open Source development is the MERN stack.

Q3. Is MERN stack a skill?

Ans. The MERN stack serves as the foundation for both frontend and backend development, incorporating React and Node.js. MERN stack developers need to be skilled in ES6+ features, asynchronous programming, and functional programming concepts to build applications effectively.

Hridhya Manoj

Hello, I’m Hridhya Manoj. I’m passionate about technology and its ever-evolving landscape. With a deep love for writing and a curious mind, I enjoy translating complex concepts into understandable, engaging content. Let’s explore the world of tech together

Leave a Comment