100 Must-Know MongoDB Interview Questions and Answers 2025

MongoDB Fundamentals

1.
What is MongoDB and what are its main features?
2.
How does MongoDB differ from relational databases?
3.
Can you describe the structure of data in MongoDB?
4.
What is a Document in MongoDB?
5.
How is data stored in collections in MongoDB?
6.
Describe what a MongoDB database is.
7.
What is the default port on which MongoDB listens?
8.
How does MongoDB provide high availability and disaster recovery?
9.
What are indexes in MongoDB, and why are they used?
10.
What is the role of the id field in MongoDB documents?

CRUD Operations

11.
How do you create a new MongoDB collection?
12.
What is the syntax to insert a document into a MongoDB collection?
13.
Describe how to read data from a MongoDB collection.
14.
Explain how to update documents in MongoDB.
15.
What are the MongoDB commands for deleting documents?
16.
Can you join two collections in MongoDB? If so, how?
17.
How do you limit the number of documents returned by a MongoDB query?
18.
What is the difference between find() and findOne() in MongoDB?
19.
How can you achieve pagination in MongoDB?
20.
What are the differences between MongoDB’s insertOne and insertMany methods?

Indexing and Aggregation

21.
Describe a compound index in MongoDB.
22.
What is the aggregation pipeline in MongoDB?
23.
How can you create an index in MongoDB and when should you do it?
24.
Explain how MongoDB’s $match, $group and $sort operators work in an aggregation pipeline.
25.
What is the purpose of the explain() method?

Replication and Sharding

26.
Can you explain MongoDB’s replication?
27.
Describe the purpose and components of a replica set.
28.
What is sharding in MongoDB and when would you use it?
29.
How does MongoDB perform automatic failover?
30.
Describe the difference between horizontal scaling and vertical scaling, and how MongoDB supports them.

Performance and Optimization

31.
How does MongoDB handle large data volumes?
32.
What strategies can you use to diagnose and address performance issues in MongoDB?
33.
How do you ensure that indexes fit into RAM?
34.
Can you explain MongoDB’s write concern?
35.
What is a covered query in MongoDB?

MongoDB Security

36.
What are the security features available in MongoDB?
37.
How do you enable authentication in MongoDB?
38.
Describe role-based access control in MongoDB.
39.
Explain how to encrypt MongoDB data.
40.
Can you set up MongoDB to use TLS/SSL for connections?

MongoDB Storage Engines

41.
What are the different storage engines available in MongoDB?
42.
How does the WiredTiger storage engine differ from MMAPv1?
43.
Can you switch between storage engines in a MongoDB database?

Advanced MongoDB Concepts

44.
What is the oplog in MongoDB, and how does it work?
45.
How do you use the $lookup operator in MongoDB?
46.
Can you explain the role of a mongos server in a sharded MongoDB architecture?
47.
What is journaling in MongoDB and why is it important?
48.
Explain the GridFS specification in MongoDB.

MongoDB Schema Design

49.
How does schema design impact performance in MongoDB?
50.
Compare embedding vs. linking documents in MongoDB.
51.
What factors do you consider when designing a schema for MongoDB?
52.
How do you handle one-to-many relationships in MongoDB data modeling?

MongoDB Management and Maintenance

53.
How do you perform backups in MongoDB?
54.
What techniques can be used to restore a MongoDB database?
55.
How would you monitor the performance of a MongoDB instance?
56.
What factors would lead you to defragment a MongoDB collection?

Working with Data Types

57.
What are the different data types supported in MongoDB?
58.
How does MongoDB store different types of numerical data?
59.
How does MongoDB handle DateTime data types?
60.
Can you store multimedia files directly in MongoDB?

MongoDB and Programming

61.
How do you connect to a MongoDB database from a Python script?
62.
What is Mongoose and how does it relate to MongoDB?
63.
Can you create and use stored procedures in MongoDB?
64.
Describe how to use the Mongo Shell for database operations.

MongoDB Drivers and ODMs

65.
What is the purpose of MongoDB ODM / ORM frameworks?
66.
How can you perform MongoDB operations using Node.js?
67.
List some popular libraries for integrating MongoDB with web applications.

MongoDB and Big Data

68.
How is MongoDB used in big data analytics?
69.
Can MongoDB handle real-time analytics workloads?
70.
How do you stream large quantities of data into and out of MongoDB?

MongoDB Internals

71.
How does MongoDB handle locking and concurrency?
72.
What is the relationship between BSON and MongoDB?
73.
Can you explain the concept of a cursor in MongoDB?
74.
How does MongoDB manage memory?

MongoDB Deployment

75.
What are some best practices for securing a MongoDB instance?
76.
How do you scale a MongoDB deployment?
77.
What is Ops Manager in MongoDB?

MongoDB Errors and Troubleshooting

78.
How do you troubleshoot a slow-running query in MongoDB?
79.
What could cause a MongoServerError: E11000 duplicate key error?
80.
How would you handle a scenario where the MongoDB service won’t start?

MongoDB in the Cloud

81.
What are some MongoDB cloud-hosted solutions?
82.
How does MongoDB Atlas enhance MongoDB capabilities?

API and Tools

83.
Describe the use of Compass in MongoDB.
84.
Explain the use of Robo 3T (formerly Robomongo).
85.
Can you work with MongoDB using the command line? If so, how?

Contemporary MongoDB Challenges and Considerations

86.
What factors to consider when deploying MongoDB in a containerized environment?
87.
How does MongoDB work with microservices architectures?
88.
What are change streams in MongoDB?

MongoDB Updates and Evolution

89.
What major features were added in the latest MongoDB release?
90.
How does MongoDB handle version upgrades in a production environment?

Use Cases for MongoDB

91.
In what scenarios is MongoDB favored over a relational database?
92.
What are some common patterns of data access in applications that use MongoDB?

MongoDB Query Optimization

93.
How can you prevent slow queries in MongoDB?
94.
Explain the role of the Profiler in MongoDB.
95.
How are B-tree indexes implemented in MongoDB?

Advanced Queries and Data Processing

96.
How do you handle complex transactions in MongoDB?
97.
Explain the MongoDB MapReduce operation.
98.
Can you perform text searches in MongoDB?

MongoDB Integration

99.
How can you integrate MongoDB with third-party applications?
100.
Describe how to synchronize data between SQL databases and MongoDB.

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100 MongoDB interview questions

What is MongoDB and what are its main features?

How does MongoDB differ from relational databases?

Can you describe the structure of data in MongoDB?

What is a Document in MongoDB?

How is data stored in collections in MongoDB?

Describe what a MongoDB database is.

What is the default port on which MongoDB listens?

How does MongoDB provide high availability and disaster recovery?

What are indexes in MongoDB, and why are they used?

What is the role of the id field in MongoDB documents?

How do you create a new MongoDB collection?

What is the syntax to insert a document into a MongoDB collection?

Describe how to read data from a MongoDB collection.

Explain how to update documents in MongoDB.

What are the MongoDB commands for deleting documents?

Can you join two collections in MongoDB? If so, how?

How do you limit the number of documents returned by a MongoDB query?

What is the difference between find() and findOne() in MongoDB?

How can you achieve pagination in MongoDB?

What are the differences between MongoDB’s insertOne and insertMany methods?

Describe a compound index in MongoDB.

What is the aggregation pipeline in MongoDB?

How can you create an index in MongoDB and when should you do it?

Explain how MongoDB’s $match, $group and $sort operators work in an aggregation pipeline.

What is the purpose of the explain() method?

Can you explain MongoDB’s replication?

Describe the purpose and components of a replica set.

What is sharding in MongoDB and when would you use it?

How does MongoDB perform automatic failover?

Describe the difference between horizontal scaling and vertical scaling, and how MongoDB supports them.

How does MongoDB handle large data volumes?

What strategies can you use to diagnose and address performance issues in MongoDB?

How do you ensure that indexes fit into RAM?

Can you explain MongoDB’s write concern?

What is a covered query in MongoDB?

What are the security features available in MongoDB?

How do you enable authentication in MongoDB?

Describe role-based access control in MongoDB.

Explain how to encrypt MongoDB data.

Can you set up MongoDB to use TLS/SSL for connections?

What are the different storage engines available in MongoDB?

How does the WiredTiger storage engine differ from MMAPv1?

Can you switch between storage engines in a MongoDB database?

What is the oplog in MongoDB, and how does it work?

How do you use the $lookup operator in MongoDB?

Can you explain the role of a mongos server in a sharded MongoDB architecture?

What is journaling in MongoDB and why is it important?

Explain the GridFS specification in MongoDB.

How does schema design impact performance in MongoDB?

Compare embedding vs. linking documents in MongoDB.

What factors do you consider when designing a schema for MongoDB?

How do you handle one-to-many relationships in MongoDB data modeling?

How do you perform backups in MongoDB?

What techniques can be used to restore a MongoDB database?

How would you monitor the performance of a MongoDB instance?

What factors would lead you to defragment a MongoDB collection?

What are the different data types supported in MongoDB?

How does MongoDB store different types of numerical data?

How does MongoDB handle DateTime data types?

Can you store multimedia files directly in MongoDB?

How do you connect to a MongoDB database from a Python script?

What is Mongoose and how does it relate to MongoDB?

Can you create and use stored procedures in MongoDB?

Describe how to use the Mongo Shell for database operations.

What is the purpose of MongoDB ODM / ORM frameworks?

How can you perform MongoDB operations using Node.js?

List some popular libraries for integrating MongoDB with web applications.

How is MongoDB used in big data analytics?

Can MongoDB handle real-time analytics workloads?

How do you stream large quantities of data into and out of MongoDB?

How does MongoDB handle locking and concurrency?

What is the relationship between BSON and MongoDB?

Can you explain the concept of a cursor in MongoDB?

How does MongoDB manage memory?

What are some best practices for securing a MongoDB instance?

How do you scale a MongoDB deployment?

What is Ops Manager in MongoDB?