Free MongoDB C100DEV Exam Questions

Become MongoDB Certified with updated C100DEV exam questions and correct answers

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Total 411 Questions | Updated On: Feb 19, 2026

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Question 1

You have two collections in your MongoDB database: students and grades. The students collection contains the following document:

{

"_id": ObjectId("64d5b0e5c9d95a76ac3ebed2"),

"student_id": 1,

"name": "Alice"

}

The grades collection contains the following documents:

{

"_id": ObjectId("64d5b0e5c9d95a76ac3ebed3"),

"student_id": 2,

"course": "Math",

"grade": "A"

{

"_id": ObjectId("64d5b0e5c9d95a76ac3ebed4"),

"student_id": 2,

"course": "Science",

"grade": "B"

}

You run the following aggregation query to retrieve students along with their grades:

db.students.aggregate([

{

$lookup: {

from: "grades",

localField: "student_id",

foreignField: "student_id",

as: "grades_details"

}

])

What will be the structure of the documents returned by this aggregation query for the student with student_id: 1?

A : { "_id": ObjectId("64d5b0e5c9d95a76ac3ebed2"), "student_id": 1, "name": "Alice", "grades_details": null}

B : { "_id": ObjectId("64d5b0e5c9d95a76ac3ebed2"), "student_id": 1, "name": "Alice", "grades_details": []}

C : { "_id": ObjectId("64d5b0e5c9d95a76ac3ebed2"), "student_id": 1, "name": "Alice", "grades_details": [ { "course": "Math", "grade": "A" } ]}

D : { "_id": ObjectId("64d5b0e5c9d95a76ac3ebed2"), "student_id": 1, "name": "Alice", "grades_details": [ { "course": "Math", "grade": "A" }, { "course": "Science", "grade": "B" } ]}

Answer: B

Question 2

In your database there is a collection named trips with the following document structure:

{

'_id': ObjectId("572bb8222b288919b68abf6d"),

'trip_duration': 858,

'start_station id': 532,

'end_station_id': 401,

'bike_id': 17057,

'start_station_loc': { type: 'Point', coordinates: [ -73.960876, 40.710451 ] },

'end_station_loc': { type: 'Point', coordinates: [ -73.98997825, 40.72019576 ] },

'start_time': ISODate("2016-01-01T00:09:31.000Z"),

'stop_time': ISODate("2016-01-01T00:23:49.000Z")

}

How can you extract all trips from this collection ended at stations that are to the west of the -73.5 longitude coordinate?

A : db.trips.find( { 'end_station_loc.coordinates.0': { $gt: -73.5 } } )

B : db.trips.find( { 'coordinates': { $lt: -73.5 } } )

C : db.trips.find( { 'end_station_loc.coordinates.0': { $lt: -73.5 } } )

D : db.trips.find( { 'end_station_loc.coordinates.1': { $lt: -73.5 } } )

Answer: C

Question 3

In a MongoDB database with referenced relationships, what is the advantage of using a separate collection for each entity over using a single collection for all entities?

A : Improved maintainability and reduced complexity of updates to related entities.

B : Improved query performance and reduced complexity of updates to related entities.

C : Improved maintainability and increased scalability.

D : Improved query performance and increased scalability.

Answer: A

Question 4

In a MongoDB database, you have a collection named orders that contains information about various product orders placed by customers. Each document in the collection has the following structure:

{

"customerID": "",

"orderID": "",

"product": "",

"quantity": ,

"price": ,

"date": "",

"status": ""

}

You are required to write an aggregation query that retrieves all orders placed by customers where the quantity of ordered items is greater than 100 and the status of the order is "delivered". Which of the following $match stages would you use to achieve this? Select the best option.

A : { "$match": { "quantity": { "$gt": 100 }, "status": "delivered" } }

B : { "$match": { "quantity": { "$lt": 100 }, "status": "delivered" } }

C : { "$match": { "quantity": { "$gt": 100 }, "status": { "$eq": "delivered" } } }

D : { "$match": { "quantity": { "$gte": 100 }, "status": "delivered" } }

Answer: A

Question 5

When sharding a MongoDB collection, what is the main factor that determines the distribution of data across shards?

A : The location of the client issuing the query

B : The number of documents in the collection

C : The size of each document

D : The value of a shard key

Answer: D

Page: 1 / 83

Total 411 Questions | Updated On: Feb 19, 2026

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