It is hard to find any such industry where the need for skilled and experienced MERN stack developers is less. Learning through simple and easy content, followed by quizzes and assignments, not only on the MERN stack but also on other related concepts, makes your concepts stronger.Â
There have always been expectations of candidates to understand the basics and be able to solve problems in the real world. With a little effort in practising MERN interview questions and related real-time scenarios, you can prove your potential to develop scalable applications. If you want to change your career, then our MERN full stack developer course, along with other full stack developer courses, will help you learn the concepts and be the best in interviews.
What exactly is the MERN stack certification exam?
The MERN stack test is a quiz on your knowledge in MongoDB, Express.js, React and Node.js. It evaluates your fullâstack web development skills based on the application of these technologies as aâbroad toolset. Clearing it signifiesâthat you are capable of handling modern web development roles and advancing your career.
Best 15 MERN Interview Questions for Beginners
So, if you are a fresher and you are preparing forMERN stack interview questions, then you should start with the basics.
Q1. What is the MERNâstack?
MERN isâMongoDB, Express.js, Node.js, and React. - The four of them combined â they provide a complete JavaScript-based solution for full-stack development.
Q2. What is MongoDBâs purpose in the MERNâstack?
MongoDB holds application data in a flexible, document-basedâway.
- Pro tipsâfor your interview:
- Schema-less design.
- Horizontal scalability.
- Simple Node.js integration.
Q3. Explain Node.jsâand its need.
Node.js is a JavaScript frameworkâthat is based on the V8 engine (It is the engine that powers Google Chrome). You can unsurprisingly write JavaScript on the server â itâs designed to be event-driven and non-blocking, and forâuse with applications that are event-based or that use a lot of I/O.
Q4. What is JSX in React?
JSX is a syntax extension that allows writing HTML-like code in JavaScript, compiled into React functions.
Q5. What is the difference between props and state in React?
Props are immutable inputs passed to components, while state is mutable data managed within a component.
Q6. What is JSX in React? Â
JSX is a type of syntaxâwhich looks very similar to XML or HTML. It is compiled to React function calls, which results in easier-to-read componentsâ, and we keep our UI logic close to the elements we are building.
Q7. What is the differenceâbetween props and state in React? Â
Props are the data which are passed down from parent to child â they are read-onlyâand immutable. State is information that a componentâmaintains itself, and can change over time in response to user input. Props are external and controlled by whatever renders the component; state is internalâto the component.
Q8. What is a component in React? Describe functionalâand class components. Â
Components are the building blocks of a Reactâapplication; they are reusable.
- Functional components areâjust functions that return UI and can use Hooks to have state and other functionalities related to the lifecycle.
- Class components are ES6 classes where you defineâyour component by extending React.
- Component class, lifecycle methods and these States are used to manage data.
- Functional components areâpreferred today because Hooks make them powerful and simpler to maintain.
Q9. What is the virtual DOM, and how does itâwork? Â
Virtual DOM is a copy of the realâDOM, but itâs virtual. When differences are there, React applies a diffing algorithm to the new virtual DOM and old virtual DOM and then makes real DOM updatesâonly where the two virtual DOMs are different. This leadsâto performant updates and renders, especially in large applications.
10. What are hooks in React? Name a few commonly used hooks.
Hooks let functional components use state and lifecycle features. Common hooks: useState, useEffect, useContext.
Q11. Couldâyou describe what a REST API is? Â
REST API is an applicationâprogramming interface that uses HTTP requests to GET, PUT, POST and DELETE data. It operates on resourcesââ a resource is (usually) an object represented in JSON â and lets developers work with those resources in a uniform, predictable way.
Q12. What doâwe mean by middleware in Express.js?? Â
We defineâmiddleware in Express.js as a series of functions that have access to the request and response objects, the next function in the applicationâs request-response cycle and can end that cycle. They perform background functions like authentication, logging, parsing data or errorâhandling, and they are called in a stack to receive a request and send a response.
Q13. What is npm,âand why is it important?
- Default package manager for Node.js projects
- Managesâdependencies and maintains version control
- Ties developers to a vast openâsource community of reusable modules andâcompetent peers.
Q14. Whatâis JSON, and where do I use it in the MERN application?
JSON is a lightweight format forâholding data and is used in API responses, configuration, and MongoDB documents.
Q15. What is CORS, and why doâyou need it?
CORS enables servers to specify whoâcan access their assets. Itâs important if the front andâback are different hosts from different origins.
Top 15 MERN Interview Questions forâExperienced Developers
Here are the best MERN stack interview questions for experienced professionals based on research:
Q1. How are authentication and authorisationâhandled in the MERN Stack?
They are handledâvia JWT tokens, Express middleware, and role-based access.
- Interview hints:
- JWTâtokens.
- Middlewareâvalidation.
- Role-basedâpermissions.
Q2. Whatâare higher-order components in React?
HOCs are functions that take a component and return a new component with additionalâpropsÂ
3. How do you optimize performance in a React app?
Useâmemoisation, lazy loading, and efficient state management.
Q4. Whatâis Redux, and why do I need it?
Redux deals with theâintricate state in numerous components.
- Interview hints:
- Centralisedâstore.
- Predictable state changes.
- Asynchronousâmiddleware.
Q5. What is the difference betweenâuseEffect and use LayoutEffect?
Use Effect executes asynchronously afterârendering; useLayoutEffect is executed synchronously after DOM mutations.
Q6. How Do MongoDB Indexes Work andâWhy Are They Important?
Indexes make queries runâfaster, so they donât need to scan every document.
Q7. What are aggregation pipelinesâin MongoDB?
Pipelines operate on the input dataâin stages for filtering, grouping, and analysing.
8. How to do error handlingâin a Node.js app?
Use try-catch, errorâmiddleware, and a logging tool.
Important points to remember for an Interview:
- Centralised middleware.
- Async errorâhandling.
- Logging.
Q9. What is server-side rendering, andâcan you do it with React?
SSRâproduces HTML on the server. Next.js and similar frameworks support SSR.
10. How to secure aâMERN application?
Use HTTPS, sanitise inputs, and implementâauthentication properly.
Q11. What is JWT, and how can I useâit in MERN?
JWTs are created for login, stored client-side,âand verified using middleware.
Q12. How do you useâRedux in the MERN project environment Variables?
Use .env files+dotenv package. Important points forâthe interview:
- dotenv usage.
- Security.
- Flexibility inâconfiguration.
Q13. What is asynchronous programming inâNode.js?
Using callbacks, promises,âasync/await in Node.js for non-blocking operations.
Q14. So, howâwould you serve a production MERN app?Â
Host backend on AWS/Heroku, serve React build files, and set environmentâvariables.
Q15. ExplainâMVC architecture in MERN?
- Model: MongoDB.
- View: React.
- Controller:âExpress + Node.js.
Tips for MERN Stack Interviews For Freshers and ExperiencedâDevelopers
At Srijan Institute, we focus on bringing youâthe best of the basics and the advanced skills.
Master the Basics
Revise fundamentalâtopics and keep practising small projects. A strong foundation will enable you to answer questions with confidenceâ, and stronger answers reduce the chances of making common mistakes.
Practice Real-World Projects
Develop appsâwith authentication, CRUD, and APIs. Highlighting your projects shows that youâhave practical knowledge and can solve problems.
Stay Updated with Latest Trends
Keep an eye on all the updates of React, MongoDB,âand Node.js. Staying up-to-date in these areas demonstratesâthat you are flexible and have an understanding of what is considered best practice in the field.
Common Mistakes Candidates Make in MERN Interviews
There are many things first-time exam takers don't pay attention to; however, those little things are equally important to keep in mind. Here are a few of them:
- Weak fundamentals:âNo basics/basics that lead to weak answers.
- Overcomplicatingâsolutions: Explaining things simply and clearly is sometimes the best.
- No practical examples: Employers prefer real-world applications toâtheory.
- Poor communication: Answers to technical questions should be Explained Confidently and clearly. Goodâcommunication will definitely help you.
Resources to Prepare for MERN StackâInterviews
Preparation is a combination of focused learning, practice, and exposureâto actual interview situations. At Srijan Institute, we suggest the combination of classâlessons, reading materials, and mock practice.
Enrolling in a MERN Full Stack DeveloperâCourse
The well-organised course content facilitates guided learning and instructor support to complete hands-on projects, honing the applicationâskills.
Practice with Mock Interviews andâTests
Practice interviews andâcoding challenges all come together to help you demonstrate your skills when youâre under pressure.
Conclusion
You have to know the basics and the advanced topics whenâyou are preparing for MERN stack interview questions. Atâ
Srijan Institute, we mould the aspirants for the same through our Courses, Hands-on practicals, and Mock Interviews. Whether youâare going to appear for MERN stack interview questions for freshers or advanced MERN interview questions for experienced developers, keep on practising and having a clear thought will definitely get you through.
FAQs Related to MERN Stack Interview Questions
Q1. How longâdoes it take to prepare for a MERN interview?
Beginners may need 2-3 months of continuousâpreparation, while experienced developers can concentrate on brushing up on advanced topics.
Q2. Do companiesâexpect freshers to know advanced MERN concepts?
Notâusually. Freshers are tested on the basics of subjects, but knowing advanced areas always helps and can giveâyou an edge.
Q3. Whatâprojects should I present in a MERN interview?
Feature projects such as common CRUD, authentication, e-commerceâetc which are indirectly practical.
Q4.âHow much DSA (Data Structures and Algorithms) is required for MERN interviews?
Focusing on stack knowledge, while MERN Interviews focus onâstack knowledge, many companies are also conducting Interviews on DSA to test problem-solving ability.
Q5. If I have a different tech background, can I make theâswitch to MERN development?
Yes. A career switch is easy in the other direction, too, from a non-tech background, and professionals from other domains as well. Since full-stack is an easier path to becoming a MERN stack developer, with stepwise learning.
