Top 40 MongoDB Interview Questions for 2024 with Answers

Mradul Mishra
Table of Contents

Are you preparing for a MongoDB interview in 2024? MongoDB continues to be a popular choice for modern application development, making it essential for aspiring developers and database administrators to be well-versed in its concepts and practices. To help you prepare effectively, we've compiled a comprehensive list of the top 40 MongoDB interview questions along with detailed answers.


1. What is MongoDB?

MongoDB is a NoSQL database program, which uses JSON-like documents with optional schemas.

2. What are the key features of MongoDB?

MongoDB features include high performance, high availability, horizontal scalability, and easy scalability.

3. Explain BSON in MongoDB.

BSON stands for Binary JSON. It is a binary-encoded serialization of JSON-like documents used in MongoDB.

4. What is a replica set in MongoDB?

A replica set is a group of MongoDB servers that maintain the same data set, providing redundancy and high availability.

5. What is sharding in MongoDB?

Sharding is the process of distributing data across multiple machines to support deployments with very large data sets and high throughput operations.

6. What is a collection in MongoDB?

A collection in MongoDB is a group of documents similar to a table in a relational database.

7. What is a document in MongoDB?

A document in MongoDB is a set of key-value pairs, similar to a row in a relational database.

8. How can you create a database in MongoDB?

You can create a database in MongoDB using the use command followed by the database name.

9. What is the syntax to insert a document in MongoDB?

To insert a document in MongoDB, you can use the insertOne() or insertMany() method.

10. How do you update documents in MongoDB?

Documents in MongoDB can be updated using the updateOne() or updateMany() methods.

11. Explain the aggregation framework in MongoDB.

The aggregation framework is a data processing pipeline for MongoDB documents that allows users to perform operations like filtering, grouping, and transforming data.

12. What is the syntax for creating an index in MongoDB?

The syntax for creating an index in MongoDB is db.collection.createIndex(keys, options).

13. What is a covered query in MongoDB?

A covered query is a query in MongoDB where all the fields in the query are part of an index, allowing MongoDB to fulfill the query using only the index without examining the actual documents.

14. Explain the concept of indexing in MongoDB.

Indexing in MongoDB is the process of creating indexes on fields to improve query performance.

15. What are the types of indexes available in MongoDB?

MongoDB supports various types of indexes, including single field, compound, multikey, text, and geospatial indexes.

16. How do you drop a collection in MongoDB?

You can drop a collection in MongoDB using the drop() method.

17. What is a TTL index in MongoDB?

A TTL (Time-To-Live) index in MongoDB is a special type of index that automatically deletes documents from a collection after a certain period of time.

18. Explain the GridFS in MongoDB.

GridFS is a specification for storing and retrieving large files in MongoDB, broken into smaller chunks for efficient storage.

19. What is the MongoDB Atlas?

MongoDB Atlas is a fully managed cloud database service provided by MongoDB, offering automatic scaling, security features, and data backup.

20. How do you perform a backup in MongoDB?

Backups in MongoDB can be performed using tools like mongodump or through MongoDB Atlas's backup feature.

21. Explain the difference between MongoDB and SQL databases.

MongoDB is a NoSQL database, while SQL databases are relational databases. MongoDB uses a flexible schema, whereas SQL databases have a fixed schema. MongoDB uses JSON-like documents, while SQL databases use tables with rows and columns.

22. What is the use of db.stats() in MongoDB?

db.stats() is a MongoDB command used to retrieve statistics about the current database, such as the number of collections, indexes, and storage size.

23. How do you create an aggregation pipeline in MongoDB?

An aggregation pipeline in MongoDB is created using the aggregate() method, where you pass an array of aggregation stages.

24. Explain the concept of MapReduce in MongoDB.

MapReduce is a data processing paradigm used in MongoDB to perform aggregation operations on large datasets.

25. How do you enable authentication in MongoDB?

Authentication in MongoDB can be enabled by starting the MongoDB server with the --auth option and creating user accounts with appropriate privileges.

26. What is the role of WiredTiger storage engine in MongoDB?

WiredTiger is the default storage engine in MongoDB, responsible for managing data storage, compression, and concurrency control.

27. How do you perform text search in MongoDB?

Text search in MongoDB can be performed using the $text operator along with the text index.

28. What is the use of the explain() method in MongoDB?

The explain() method in MongoDB provides information about the query execution plan, including the indexes used and the number of documents examined.

29. Explain the concept of transactions in MongoDB.

Transactions in MongoDB allow you to perform multiple operations on multiple documents within a single transaction, ensuring atomicity, consistency, isolation, and durability.

30. What is the role of the mongod process in MongoDB?

The mongod process is the primary daemon process for MongoDB, responsible for handling database operations and interactions.

31. How do you limit the number of documents returned in a MongoDB query?

You can limit the number of documents returned in a MongoDB query using the limit() method.

32. What is the use of the $lookup stage in MongoDB aggregation?

The $lookup stage in MongoDB aggregation performs a left outer join between two collections, allowing you to retrieve related documents from another collection.

33. Explain the role of the mongos process in MongoDB.

The mongos process is the MongoDB shard router, responsible for routing client requests to the appropriate shard in a sharded cluster.

34. How do you perform a range query in MongoDB?

Range queries in MongoDB can be performed using query operators like $gt, $lt, $gte, and $lte.

35. What is the role of the mongo shell in MongoDB?

The mongo shell is a command-line interface for MongoDB, allowing users to interact with the database using JavaScript-like syntax.

36. How do you drop an index in MongoDB?

You can drop an index in MongoDB using the dropIndex() method.

37. Explain the role of the configsvr process in MongoDB.

The configsvr process in MongoDB is responsible for storing metadata and configuration settings for sharded clusters.

38. What is the use of the mongodump tool in MongoDB?

The mongodump tool in MongoDB is used to create binary backups of the entire database or specific collections.

39. How do you perform an upsert operation in MongoDB?

Upsert operations in MongoDB can be performed using the update() method with the upsert option set to true.

40. What is the role of the mongorestore tool in MongoDB?

The mongorestore tool in MongoDB is used to restore data from binary backups created with mongodump.

These are just the first 40 questions from our list of the top 50 MongoDB interview questions for 2024. Stay tuned for the next part of this blog post where we'll cover the remaining questions along with detailed answers! If you're preparing for a MongoDB interview, be sure to study these questions thoroughly to enhance your chances of success.

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