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: Mar 08, 2026

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Question 1

In MongoDB, the $out operator is commonly used within an aggregation pipeline. Which of the following statements accurately describes the functionality and usage of the $out operator?

A : $out operator is used to output the results to a specified collection.

B : $out operator can be used to output the results to a collection in a different MongoDB database.

C : $out operator is used to export data directly to a file.

D : $out operator is used to read data from multiple collections in a single command.

Answer: A

Question 2

There is a collection named products in MongoDB database. Your coworker wants to know how many products are in this collection (number of documents in the collection). Which query should you use? (Select two)

A : db.products.total()

B : db.products.countAll()

C : db.products.countDocuments()

D : db.products.aggregate()

E : db.products.find().count()

Answer: C,E

Question 3

Which of the following stages do you need to use to randomly select 10 documents from a specific collection?

A : { $rand: { size: 10 } }

B : { $sample: { get: 10 } }

C : { $sampleRate: { size: 10 } }

D : { $sample: { size: 10 } }

Answer: D

Question 4

You manage a MongoDB collection called inventory that stores documents for a store's inventory. Each document has the fields item, category, and quantity. You want to ensure that an item is always present in the collection, even if it needs to be inserted. Specifically, if the item "notebook" in the "Stationery" category does not exist, it should be inserted with a quantity of 50. If it does exist, its quantity should be updated to 50. You plan to use the following command:

db.inventory.updateOne(

{ "item": "notebook", "category": "Stationery" },

{ $set: { "quantity": 50 } },

{ upsert: true }

)

What will happen after executing this command if there is no "notebook" item in the "Stationery" category in the inventory collection?

A : A new document will be inserted with only quantity: 50, as other fields (item and category) are not mentioned in the $set operator.

B : Nothing will happen because the $set operator only updates existing documents and cannot insert new ones.

C : A new document will be inserted with quantity: 50, but the item field will be set to null.

D : A new document will be inserted with item: "notebook", category: "Stationery", and quantity: 50.

Answer: D

Question 5

In a MongoDB collection named orders, you are tasked with retrieving a subset of documents that fulfill specific criteria. Each document in this collection contains the following fields: customerId, orderId, orderDate, and orderDetails (an embedded document with fields: product, quantity, unitPrice). You are required to fetch all orders made by the customer with a customerId of 1234 on a specific date 2023-04-12, and only return the orderId, orderDate, and product from orderDetails. Which of the following MongoDB queries would accurately fulfill these requirements?

A :

B :

C :

D :

Answer: A

Page: 1 / 83

Total 411 Questions | Updated On: Mar 08, 2026

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