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Want to learn MongoDB step by step with hands-on practice?
This guide includes beginner-friendly MongoDB practice questions, real-world exercises, and structured learning to help you master database concepts.
👉 Start here: MongoDB Practice Questions with Answers (Complete Series)
You will learn:
Bookmark this guide and start practicing today.
Welcome to Part 8 of the MongoDB Practice Series.
This is a real-world project practice where you will combine everything you learned:
This challenge simulates building a real application database.
You are designing a database for an online learning website.
The system must manage:
Problem:
Design collections for the system.
Solution Example:
// Users Collection
{
_id: 1,
name: "Amit",
email: "amit@example.com",
country: "India"
}
// Courses Collection
{
_id: 101,
title: "MongoDB Basics",
price: 1500,
category: "Database"
}
// Enrollments Collection
{
_id: 5001,
user_id: 1,
course_id: 101,
enrollmentDate: new Date()
}
// Payments Collection
{
_id: 9001,
user_id: 1,
amount: 1500,
paymentStatus: "Completed"
}
Learning Goal: Understand when to use referencing for scalability.
Task:
Practice: Use insertMany() for efficiency.
db.courses.find({ category: "Database" })
db.users.find({ country: "India" })
db.enrollments.find()
.sort({ enrollmentDate: -1 })
.limit(5)
db.enrollments.aggregate([
{
$group: {
_id: "$course_id",
totalEnrollments: { $sum: 1 }
}
}
])
db.payments.aggregate([
{
$match: { paymentStatus: "Completed" }
},
{
$group: {
_id: null,
totalRevenue: { $sum: "$amount" }
}
}
])
Create indexes for better performance:
// Faster user search
db.users.createIndex({ email: 1 })
// Faster enrollment lookup
db.enrollments.createIndex({ user_id: 1 })
// Faster course filtering
db.courses.createIndex({ category: 1 })
Learning Goal: Improve query performance in large systems.
Design a reporting query that:
Try solving it by combining:
This is a real interview-level challenge.
If you completed all 8 parts of this MongoDB Practice Series, you now understand:
You are now ready to build real MongoDB applications.
See: Complete MongoDB Practice SeriesWelcome to Part 7 of the MongoDB Practice Series.
In this lesson, you will learn how to improve query performance using indexes.
Indexes help MongoDB find data faster, especially in large collections.
Problem:
Create an index on the email field in the users collection.
Solution:
db.users.createIndex({ email: 1 })
Learning Goal: Improve search performance on email queries.
Problem:
Check which indexes exist in the products collection.
Solution:
db.products.getIndexes()
Learning Goal: Understand existing indexing structure.
Problem:
Remove the index on the price field.
Solution:
db.products.dropIndex({ price: 1 })
Learning Goal: Learn how to manage indexes properly.
Problem:
Create an index on both category and price fields.
Solution:
db.products.createIndex({ category: 1, price: -1 })
Learning Goal: Understand compound indexes for multi-field queries.
Problem:
The following query is slow:
db.orders.find({ customerName: "Amit" })
Task:
Improve its performance.
Solution:
db.orders.createIndex({ customerName: 1 })
Learning Goal: Use indexing to speed up frequently searched fields.
Problem:
Check how MongoDB executes a query.
Solution:
db.products.find({ price: { $gt: 1000 } }).explain("executionStats")
Learning Goal: Analyze query performance using explain.
You have a large users collection with millions of records.
Design indexes for the following queries:
Think carefully:
Try designing the indexing strategy before checking any solution.
In Part 8 of the MongoDB Practice Series, we will practice:
Stay tuned for the final advanced practice level!
See: "Complete MongoDB Practice Series”