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 collection named orders with the following documents:
{
   "_id" : ObjectId("5f0a7e80d8c9c7b5a48c49e1"),
   "order_number" : 1001,
   "customer_id" : "CUST-001",
   "order_date" : ISODate("2022-01-01T00:00:00Z"),
   "total_amount" : 199.99
},
{
   "_id" : ObjectId("5f0a7e80d8c9c7b5a48c49e2"),
   "order_number" : 1002,
   "customer_id" : "CUST-002",
   "order_date" : ISODate("2022-02-01T00:00:00Z"),
   "total_amount" : 299.99
},
{
   "_id" : ObjectId("5f0a7e80d8c9c7b5a48c49e3"),
   "order_number" : 1003,
   "customer_id" : "CUST-003",
   "order_date" : ISODate("2022-03-01T00:00:00Z"),
   "total_amount" : 399.99
}
What is the query to create a compound index on the "customer_id" (ascending) and "order_date" (descending) fields in the orders collection?


Answer: C
Question 2

Consider a collection named students with the following document:
{
   "_id" : ObjectId("5f0a7e80d8c9c7b5a48c49e1"),
   "name" : "Alice",
   "age" : 21,
   "courses" : [
      {
         "name" : "Math",
         "grade" : 89
      },
      {
         "name" : "Science",
         "grade" : 92
      }
   ]
}
What is the query to update the grade of the "Math" course for the student with "_id" equal to ObjectId("5f0a7e80d8c9c7b5a48c49e1") to 95?


Answer: C
Question 3

Which of the following statements are true regarding the MongoDB Aggregation Framework and pipelines? (Select two)


Answer: A,E
Question 4

Consider a MongoDB collection named products which has documents in the following format:
{
    "_id" : ObjectId("5f5b0d2f3e3dfbcc11c84444"),
    "name" : "Smartphone",
    "brand" : "Apple",
    "category" : "Electronics",
    "price" : 1000,
    "discount" : 0.1
}
What is the correct syntax to update the "price" field of all documents in the products collection by multiplying it with (1 - discount) using the $set operator and the $multiply operator?


Answer: D
Question 5

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?


Answer: A
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Total 411 Questions | Updated On: Mar 08, 2026
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