MongoDB Interview Questions

I am sharing top 41 MongoDB Interview Questions, which will help you to crack the MongoDB Interview.

Q1:- What is MongoDB?

Ans:- MongoDB is a NoSql Database, it is based on BSON.

Q2:- Why is MongoDB not chosen for a 32-bit system?

Ans:- Mongo DB is not considered as a 32-bit system because for running the 32-bit MongoDB, with the server, information and indexes require 2 GB. That is why it is not used in 32-bit devices

Q3:- How to create database?

Ans:- use databaseName

Q4:- How to drop the database?

Ans:- db.dropDatabse() command is used to drop a database.

Q5:- What is a Collection in MongoDB?

Ans- In MongoDB, a collection is a group of MongoDB documents.

Q6:- How to create collection?

Ans:- db.createCollection(name,options)

Q7:- How to drop a collection?

Ans:- db.collectionName.drop()

Q8:- How to insert a document in the collection?

Ans:- db.collectionName.insertOne() is used to add single document in the collection.
db.collectionName.insertMany() is used to add multiple documents in the collection.

Q9:- What is the use of the save() method?

Ans:- The save() method is used to replace the existing document with a new document.

Q10:- Which method is used to update the document?

Ans:- If you want to update single document then use

If you want to update Multiple documents then use

Q11:- Which method is used to remove a document from a collection?

Ans:- The remove() method is used to remove a document from a collection.

Q12:- What is MongoDB Projection?

Ans:- Projection is used to select only the necessary data. It does not select the whole data of a document.

Q13:- What is the use of the pretty() method?

Ans:- The pretty() method is used to show the results in a formatted way.

Q14:- What is the use of the limit() method?

Ans:- The limit() method is used to limit the records in the database.

Q15:- What is the syntax of the limit() method?

Ans:- The syntax of the limit() method is as follows

Q16:- What is the syntax of the sort() method?

Ans:- In MongoDB, the following syntax is used for sorting documents:
Note: 1 is used for ascending order.
-1 is used for descending order.

Q17:- What is the syntax of the skip() method?

Ans:- The syntax of the skip() method is as follows:

Q18:- How to filter the records?

Ans:- [php]
db.users.find({name: /a/}) //like ‘%a%’
db.users.find({name: /^pa/}) //like ‘pa%’
db.users.find({name: /ro$/}) //like ‘%ro’

Q19:- Which command is used to create a backup of the database?

Ans:- The mongodump command is used to create a backup of the database.

Q20:- Which command is used to restore a backup into the database?

Ans:- The mongorestore command is used to restore into the database.

Q21:- What is the use of an Index in MongoDB?

Ans:- indexes are used to increase the performance to get the records from the database.

Q22:- How to create an index in MongoDB?


Q23:- How to get the indexes from the collection?


Q24:- Define Namespace in MongoDB?

Ans:- MongoDB stores BSON objects in collections. The concatenation of the database name and the collection name (with a period in between) is called a “namespace”.

Q25:- What is Replication?

Ans:- MongoDB replication is distributed to the data across different machines.

Q26:- What is the use of GridFS in MongoDB?

Ans:- GridFS is used for storing and retrieving large files, such as audio, image, and video files.

Q27:- What is the use of Journaling in MongoDB?

Ans:- Journaling is used for safe backups in MongoDB.

Q28:- What is the use of Profiler?

Ans:- Profiler is used to show the performance characteristics of every operation against the database.

Q29:- What type of data is stored by MongoDB?

Ans:- MongoDB stores data in the form of documents, which are JSON-like field and value pairs.

Q30:- What is the purpose of Replication?

Ans:- Replication provides redundancy, and it increases data availability.

Q31:- What are Embedded documents?

Ans:- Embedded documents capture relationships between data by storing related data in a single document structure.

Q32:- What is Vertical Scaling?

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

Q33:- Define Horizontal Scaling.

Ans:- Horizontal scaling divides the dataset and distributes data over multiple servers, or shards.

Q34:- What is Aggregation pipeline?

Ans:- The aggregation pipeline is a framework for performing aggregation tasks. The pipeline is used to transform documents into aggregated results.

Q35:- What is sharding?

Ans:- Sharding is a method for distributing data across multiple machines. MongoDB uses sharding to support deployments with very large data sets and high throughput operations.

Q36:- Which are the storage engines used by MongoDB?

Ans:- MMAPv1 and WiredTiger are two storage engines used by MongoDB.

Q37:- What is the profiler in mongodb?

Ans:- MongoDB Profiler allows you to analyze all the queries which are being run by the database system.
Note:- MongoDB would be to use the query profiler to track and diagnose slow queries.

Q38:- MongoDB store data in which format?

Ans:- MongoDB uses documents to store data into the collections.

Q39:- What is replica set in MongoDB?

Ans:- A replica can be specified as a group of mongo instances that host the same data set. In a replica set, one node is primary, and another is secondary. All data is replicated from primary to secondary nodes.

Q40:- What is primary and secondary replica set in MongoDB?

Ans:- In MongoDB, primary nodes are the node that can accept write. These are also known as master nodes. The replication in MongoDB is a single master so, only one node can accept write operations at a time.
Secondary nodes are known as slave nodes. These are read-only nodes that replicate from the primary.

Q41:- What is Ad-hoc Queries?

Ans:- Ad-hoc queries are the queries not known while structuring the database. So, MongoDB provides ad-hoc query support which makes it so special in this case.