Most Important Node.js and MongoDB Interview Questions
Most Important Node.js and MongoDB Interview Questions: Prepare with top questions on Node.js and MongoDB to ace your interviews and secure your dream job!
1. What is Node.js?
Node.js is a runtime environment that allows you to run JavaScript on the server side. It is built on Chrome’s V8 JavaScript engine.
2. What are the key features of Node.js?
Asynchronous and Event-Driven
Single-Threaded but Scalable
Non-blocking I/O
Built-in Libraries for various tasks (e.g., HTTP, File System)
3. What is the event loop in Node.js?
The event loop is a mechanism that handles asynchronous operations by executing the callbacks after completing tasks like I/O operations.
4. What is NPM?
NPM (Node Package Manager) is a package manager for Node.js that allows you to install, share, and manage JavaScript packages.
5. What is the difference between require() and import?
require() is used in CommonJS, while import is used in ES6 modules.
Intermediate Questions and Answers
6. How does Node.js handle asynchronous operations?
Through callbacks, promises, and async/await.
7. What are streams in Node.js?
Streams are objects that enable reading or writing data piece-by-piece, rather than loading the entire data into memory.
8. What is the Buffer class used in Node.js?
The Buffer class is used to handle binary data.
9. What is the difference between setImmediate() and process.nextTick()?
setImmediate() schedules code execution at the end of the current event loop, while process.nextTick() executes code before the next iteration of the event loop begins.
10. What are global objects in Node.js?
Examples: __dirname, __filename, Buffer, global, etc.
Advanced Questions and Answers
11. What is the purpose of clustering in Node.js?
Clustering allows you to create multiple instances of your application to utilize multiple CPU cores.
12. How does Node.js manage memory?
Through V8’s garbage collection mechanism.
13. What is middleware in Node.js?
Middleware is a function executed during the request-response cycle.
14. How can you improve the performance of a Node.js application?
Use clustering, caching, and load balancing.
Optimize database queries.
Use asynchronous programming.
15. What is the difference between spawn() and exec() in Node.js?
spawn() launches a new process with a stream, while exec() buffers the entire output.
MongoDB Interview Questions and Answers
Basic Questions
16. What is MongoDB?
MongoDB is a NoSQL database that stores data in a flexible, JSON-like format called BSON.
17. What are the key features of MongoDB?
Schema-less database
High performance
Scalability via sharding
Rich query language
18. What is the difference between SQL and NoSQL databases?
SQL databases use structured data with schemas, while NoSQL databases are schema-less and allow unstructured data.
19. What is a collection in MongoDB?
A collection is a group of MongoDB documents, equivalent to a table in relational databases.
20. What is a document in MongoDB?
A document is a record in MongoDB stored in JSON-like format.
Intermediate Questions and Answers
21. How does MongoDB ensure high availability?
Through replica sets.
22. What is sharding in MongoDB?
Sharding is the process of distributing data across multiple machines to ensure scalability.
23. What is an index in MongoDB?
An index improves the performance of queries by providing faster access to documents.
24. What is aggregation in MongoDB?
Aggregation is a process used to perform operations like filtering, grouping, and sorting on data.
25. How does MongoDB handle transactions?
MongoDB supports multi-document ACID transactions from version 4.0 onwards.
Advanced Questions and Answers
26. What is the difference between embedded and referenced relationships in MongoDB?
Embedded stores related data in a single document, while referenced stores data in separate documents linked via references.
27. How do you perform data modeling in MongoDB?
By understanding the relationships, usage patterns, and structure of the data.
28. What are MongoDB Atlas and Compass?
Atlas is MongoDB’s cloud database service. Compass is a GUI tool for interacting with MongoDB.
29. What is a capped collection in MongoDB?
A fixed-size collection that automatically overwrites the oldest entries when it reaches its limit.
30. How can you back up data in MongoDB?
Using mongodump and mongorestore.
Express.js Interview Questions
Basic Questions
31. What is Express.js?
A web application framework for Node.js used to build web and mobile applications.
32. What are the features of Express.js?
- Middleware support
- Routing
- Template engines
- RESTful APIs
33. What is middleware in Express.js?
Functions that execute during the request-response cycle.
34. How do you install Express.js?
Run npm install express.
35. What is the difference between app.use() and app.get() in Express.js?
app.use() is used for middleware, while app.get() handles GET requests.
Intermediate Questions
36. How do you handle 404 errors in Express.js?
javascript
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app.use((req, res) => {
res.status(404).send(‘Page not found’);
});
37. What is the difference between req.params and req.query?
req.params captures route parameters, while req.query captures query string parameters.
38. How do you enable CORS in Express.js?
Use the cors middleware:
javascript
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const cors = require(‘cors’);
app.use(cors());
39. How do you use templates in Express.js?
Set the view engine and render templates:
javascript
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app.set(‘view engine’, ‘ejs’);
app.render(‘index’);
40. What is routing in Express.js?
Routing refers to defining URL endpoints and handling HTTP methods.
Advanced Questions
41. How do you secure an Express.js application?
Use Helmet, HTTPS, rate limiting, and sanitize inputs.
42. What is the difference between synchronous and asynchronous middleware in Express.js?
Synchronous middleware completes immediately, while asynchronous middleware uses next() or await.
43. How do you handle errors in Express.js?
javascript
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app.use((err, req, res, next) => {
res.status(500).send(‘Internal Server Error’);
});
44. What is a sub-router in Express.js?
A mini router is used to organize routes into separate files.
45. How do you upload files in Express.js?
Use the multer middleware.
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