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

Consider a MongoDB database managing e-commerce product data. The database has a collection named products with documents containing the fields product_id, category, price, and reviews. Each reviews field is an array of subdocuments with fields user_id, rating, and comment. You are tasked with optimizing a query that retrieves all products within a specific category that have an average rating higher than 4. The query is frequently used, and performance is critical. Which indexing strategy would best optimize this query?

A : Create a compound index on category and reviews.rating, with a partial filter expression that only includes documents where the average rating in reviews.rating is greater than 4.

B : Create a multi-key index on reviews.rating.

C : Create a compound index on category and reviews.rating.

D : Create a single index on the category field.

E : Create a compound index on category, reviews.rating, and price.

Answer: A

Question 2

Suppose you have a products collection with an index:

{ product_category: 1 }

For which of the following queries can MongoDB look at only a subset of the index entries, rather than all of the index entries?

A : db.products.find( { product_category: /A$/ } )

B : db.products.find( { product_category: /A./ } )

C : db.products.find( { product_category: /S./ } )

D : db.products.find( { product_category: /^A./ } )

Answer: D

Question 3

How can you insert a new document into a MongoDB collection named customers?

A :

B :

C :

D :

Answer: D

Question 4

Suppose you insert the following documents into a companies collection:

db.companies.insertMany([

{"name": "Facebook"},

{"name": "X"}

])

Select all true statements about this command. (Select three)

A : This command will insert one document into the collection.

B : The command will only insert the first document and skip the second because the _id field is not explicitly provided.

C : This command will insert two documents into the collection.

D : MongoDB will automatically create an _id field for each document and it will be unique.

E : The _id field is not specified in any of these documents.

Answer: C,D,E

Question 5

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

{

name: 'Wize',

relationships: [

{

is_past: false,

title: 'Head of Product',

person: {

first_name: 'Ethan',

last_name: 'Smith',

permalink: 'ethan-smith'

}

{

is_past: true,

title: 'Director, Business Development',

person: {

first_name: 'Stephanie',

last_name: 'Quay',

permalink: 'stephanie-quay'

}

{

is_past: true,

title: 'Sr. Engineer',

person: {

first_name: 'Stefan',

last_name: 'Antonowicz',

permalink: 'stefan-antonowicz'

}

]

}

Which of the following queries should you use to extract all companies that have "Co-Founder" title in relationships field (Array)?

A : db.companies.find( { relationships: { $expr: { title: 'Co-Founder' } } } )

B : db.companies.find( { relationships: { $elemMatch: { title: 'Co-Founder' } } } )

C : db.companies.find( { relationships: { $match: { title: 'Co-Founder' } } } )

D : db.companies.find( { relationships: { $eq: { title: 'Co-Founder' } } } )

Answer: B

Page: 1 / 83

Total 411 Questions | Updated On: Mar 08, 2026

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