Top MongoDB Interview Questions & Answers

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mongodb interview questions


MongoDB is a free open-source cross-platform document-oriented and leading NoSQL database program. It uses JSON-like documents with schemas and provides high performance, high availability and high scalability.

As one of the most popular tools in its field, MongoDB offers a lot of career opportunities for expert professionals. You can enrol in a MongoDB certification course to enhance your career.

Here are a list of some of the commonly-asked MongoDB interview questions (with answers) that will help you to improve your chances of getting a job:


Q1. What is “Namespace” in MongoDB?


    Ans. MongoDB stores BSON (Binary Interchange and Structure Object Notation) objects in the collection. The concatenation of the collection name and database name is called a namespace.


Q2. What are the advantages of MongoDB?


Ans. Document-oriented (DO), high performance (HP), high availability (HA), easy scalability, rich query language


Q3. In which language MongoDB is written?


Ans. C++, C and JavaScript


Q4. Do MongoDB databases have tables?


Ans. No. MongoDB stores its data in collections.


Q5. What is sharding in MongoDB?


Ans. The procedure of storing data records across multiple machines is referred as Sharding.


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Q6. If you remove an object attribute, is it deleted from the database?


Ans. Yes, it is deleted.


Q7. Does MongoDB support SQL?


Ans. No. However, MongoDB does support a rich query language of its own.



Q8. Explain what is a replica set?


Ans. Replica set is a group of mongo instances that host the same data set.


Q9. Explain what is the role of profiler in MongoDB?


Ans. The database profiler collects fine grained data about MongoDB write operations, cursors, database commands on a running mongod instance.


Q10. What is Journaling in MongoDB?


Ans. In this process, a write operation occurs in mongod, which then creates changes in private view. The first block is memory and the second block is ‘my disc’. After a specified interval, which is called a ‘journal commit interval’, the private view writes those operations in journal directory (residing in the disc).


Q11. Why are data files so large in MongoDB?


Ans. MongoDB does aggressive pre-allocation of reserved space to avoid file system fragmentation, which is the reason why data files are so large.


Q12. Explain what are indexes in MongoDB?


Ans. Indexes are special structures in MongoDB, which stores a small portion of the data set in an easy to traverse form.


Q13. Explain what is the use of GridFS in MongoDB?


Ans. It is used for storing and retrieving large files such as images, video files and audio files.


Q14. Explain replica set.


Ans. It is a group of mongo instances that maintain same data set.


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Q15. What is CRUD?


Ans. Mongodb provides CRUD operations that are create, Read, Update, Delete.


Q16. Which syntax is used to create collection in mongodb?


Ans. db.collection.drop() is used to drop collection in mongodb.


Q17. What is vertical scaling?


Ans. Vertical scaling adds more CPU and storage resources to increase capacity.


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Q18. Define horizontal scaling.


Ans. It divides the data set and distributes the data over multiple servers, or shards.


Q19. Which command is used to restore the backup?


Ans. Mongorestore command is used to restore the backup.


Q20. Define auditing.


Ans. Auditing provides administrators with the ability to verify that the implemented security policies are controlling activity in the system.

These are some of the popular questions asked in a MongoDB interview. Always be prepared to answer all types of questions — technical skills, interpersonal, leadership or methodology. If you are someone who has recently started your career in MongoDB, you can always get certified in the various technique and skills needed to be an expert in the field.

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About the Author

Hasibuddin Ahmed

Hasibuddin Ahmed

Hasib is a professional writer associated with He has written a number of articles related to technology, marketing, and career on various blogs and websites. As an amateur career guru, he often imparts nuggets of knowledge related to leadership and motivation. He is also an avid reader and passionate about the beautiful game of football.