MongoDB Certified Developer Associate Practice Exam Test

Preparing for the MongoDB Certified Developer Associate exam? You’re in the right place! This practice test includes 25 multiple-choice questions designed to evaluate your knowledge of MongoDB concepts, tools, and development practices. It’s a great way to assess your understanding and prepare for the types of questions you’ll face on the actual exam.

Each question comes with the correct answer and a brief, clear explanation to reinforce your understanding. The topics covered include CRUD operations, aggregation, indexing, data modeling, replication, and MongoDB drivers. By practicing these questions, you’ll gain confidence in working with MongoDB and improve your problem-solving skills.

Whether you’re new to MongoDB or polishing your skills for certification, this practice test is a valuable resource to track your progress. Let’s get started and move closer to achieving your MongoDB Certified Developer Associate certification!

1. Which method is used to retrieve documents from a MongoDB collection?

A) find()

B) get()

C) retrieve()

D) fetch()

Answer:

A) find()

Explanation:

The find() method is used in MongoDB to retrieve documents from a collection based on a query condition.

2. What is the purpose of indexing in MongoDB?

A) Data Redundancy

B) Data Integrity

C) Improve Query Performance

D) Data Security

Answer:

C) Improve Query Performance

Explanation:

Indexing in MongoDB is used to improve the performance of search queries by creating a specific data structure that holds a portion of the collection’s data.

3. How do you update documents in a MongoDB collection?

A) update()

B) modify()

C) updateOne() or updateMany()

D) change()

Answer:

C) updateOne() or updateMany()

Explanation:

The updateOne() and updateMany() methods are used to update single or multiple documents in a MongoDB collection, respectively.

4. Which of the following is the default index created by MongoDB for every collection?

A) Primary Index

B) Secondary Index

C) Compound Index

D) _id Index

Answer:

D) _id Index

Explanation:

MongoDB automatically creates a unique index on the _id field for every collection, known as the _id Index.

5. What is the function of the $set operator in MongoDB?

A) Set Field Value

B) Query Data

C) Delete Field

D) Aggregate Data

Answer:

A) Set Field Value

Explanation:

The $set operator is used to set the value of a field in a document. If the field does not exist, $set will add a new field with the specified value.

6. Which MongoDB operator is used to group documents in an aggregation pipeline?

A) $group

B) $sort

C) $merge

D) $filter

Answer:

A) $group

Explanation:

The $group stage groups documents from a collection based on a specified identifier expression and applies an accumulator expression to each group.

7. What is the purpose of embedding documents in MongoDB?

A) Normalize Data

B) Denormalize Data

C) Index Data

D) Secure Data

Answer:

B) Denormalize Data

Explanation:

Embedding documents in MongoDB is a form of denormalization, where related data is stored within a single document structure, improving query performance.

8. How do you create a compound index in MongoDB?

A) Using the createIndex() method with multiple fields

B) Using the compoundIndex() method

C) Using the index() method with the compound option

D) It’s not possible to create compound indexes

Answer:

A) Using the createIndex() method with multiple fields

Explanation:

Compound indexes in MongoDB are created using the createIndex() method and specifying multiple fields in the index.

9. Which of the following is a correct way to model One-to-Many relationships in MongoDB?

A) Referencing

B) Embedding

C) Both A and B

D) None of the above

Answer:

C) Both A and B

Explanation:

One-to-Many relationships in MongoDB can be modeled either by embedding documents or by referencing document IDs.

10. Q: Which aggregation pipeline stage in MongoDB is used for sorting documents?

A) $sort

B) $order

C) $arrange

D) $sequence

Answer:

A) $sort

Explanation:

The $sort stage is used in the aggregation pipeline to sort input documents based on the specified sort expression.

11. How can you improve the performance of a query that retrieves documents based on a non-indexed field?

A) Use Projection

B) Use Limit

C) Create an Index

D) Use Aggregation

Answer:

C) Create an Index

Explanation:

Creating an index on the field used in the query condition can significantly improve the performance of the query.

12. Q: What is the primary function of the WiredTiger storage engine in MongoDB?

A) Data Compression

B) Data Encryption

C) Data Replication

D) Data Sharding

Answer:

A) Data Compression

Explanation:

WiredTiger is the default storage engine for MongoDB, and one of its primary functions is to provide data compression, which reduces the storage footprint of the data.

13. How does sharding help in optimizing MongoDB performance?

A) By distributing data across multiple servers

B) By compressing data

C) By replicating data

D) By indexing data

Answer:

A) By distributing data across multiple servers

Explanation:

Sharding in MongoDB is a method of distributing data across multiple servers or clusters to optimize performance, especially for large-scale databases.

14. Which of the following MongoDB methods can be used to optimize a collection by defragmenting and rebuilding the storage?

A) optimizeCollection()

B) defragCollection()

C) rebuildCollection()

D) compact()

Answer:

D) compact()

Explanation:

The compact() command is used in MongoDB to defragment and rebuild the storage for a collection, which can optimize space usage and improve performance.

15. In which scenario would you use the $hint operator in MongoDB queries?

A) To force a specific index usage

B) To provide a hint for data projection

C) To optimize data sharding

D) To give a hint for data aggregation

Answer:

A) To force a specific index usage

Explanation:

The $hint operator in MongoDB is used to force the query planner to use a specific index to fulfill the query.

16. How can you secure sensitive data in MongoDB?

A) By using Field Level Redaction

B) By using SSL/TLS for data in transit

C) By using MongoDB’s native encryption for data at rest

D) All of the above

Answer:

D) All of the above

Explanation:

Securing sensitive data in MongoDB can be achieved through field-level redaction, SSL/TLS for data in transit, and MongoDB’s native encryption for data at rest.

17. Which of the following is a valid role that can be assigned to a user in MongoDB?

A) readWrite

B) dbAdmin

C) userAdmin

D) All of the above

Answer:

D) All of the above

Explanation:

All the given options, readWrite, dbAdmin, and userAdmin, are valid roles that can be assigned to a user in MongoDB.

18. What is the purpose of journaling in MongoDB?

A) Data Analysis

B) Data Backup

C) Crash Recovery

D) Data Sharding

Answer:

C) Crash Recovery

Explanation:

Journaling in MongoDB is used to ensure data integrity and provide crash recovery by keeping a rolling log of write operations.

19. How do you backup data in a MongoDB database?

A) Using mongodump command

B) Using mongorestore command

C) Using mongoexport command

D) Using mongoshard command

Answer:

A) Using mongodump command

Explanation:

The mongodump command is used to create a binary export of the contents of a MongoDB database, which can be used for backup purposes.

20. Which MongoDB feature allows the execution of JavaScript functions in the database?

A) JS Execution

B) Stored Procedures

C) Server-side Scripts

D) MongoDB Shell

Answer:

C) Server-side Scripts

Explanation:

MongoDB supports the execution of JavaScript functions on the server-side, allowing for complex operations and logic to be executed within the database.

21. What is the purpose of the $lookup stage in the MongoDB aggregation pipeline?

A) To look up and retrieve documents

B) To perform left outer join

C) To perform right outer join

D) To lookup index usage

Answer:

B) To perform left outer join

Explanation:

The $lookup stage in the MongoDB aggregation pipeline performs a left outer join with another collection to filter and aggregate data.

22. How do you remove all documents from a MongoDB collection?

A) Using remove({})

B) Using deleteOne({})

C) Using deleteMany({})

D) Using removeAll()

Answer:

C) Using deleteMany({})

Explanation:

The deleteMany({}) method with an empty filter object can be used to remove all documents from a MongoDB collection.

23. What is the function of the oplog collection in MongoDB replication?

A) It stores the operations history

B) It stores the replication configuration

C) It stores the replicated data

D) It stores the replication errors

Answer:

A) It stores the operations history

Explanation:

The oplog (operations log) is a special capped collection that keeps a rolling record of all operations that modify the data stored in your databases in a MongoDB replica set.

24. What is the role of a majority write concern in MongoDB?

A) It ensures that writes are acknowledged by the majority of replica set members

B) It ensures that writes are acknowledged by all replica set members

C) It ensures that writes are acknowledged by any one of the replica set members

D) It does not acknowledge writes

Answer:

A) It ensures that writes are acknowledged by the majority of replica set members

Explanation:

A majority write concern in MongoDB ensures that write operations are acknowledged by the majority of members in a replica set to ensure data consistency and durability.

25. Which of the following is a benefit of using MongoDB Change Streams?

A) Real-time Data Updates

B) Data Compression

C) Data Sharding

D) Data Encryption

Answer:

A) Real-time Data Updates

Explanation:

MongoDB Change Streams allow applications to access real-time updates to data changes in a MongoDB database, enabling the development of reactive, real-time applications.