estimatedDocumentCount for speed in MongoDB - Mini Project: Build & Apply

Using estimatedDocumentCount for Fast Collection Size in MongoDB

📖 Scenario: You manage a large online store database using MongoDB. You want to quickly find out how many products are in the products collection without waiting for a slow exact count.

🎯 Goal: Build a simple MongoDB script that uses estimatedDocumentCount() to quickly get the approximate number of documents in the products collection.

📋 What You'll Learn

Create a MongoDB collection named products with 5 sample product documents.

Add a variable countThreshold to set a minimum count for alerting.

Use estimatedDocumentCount() to get the approximate number of documents in products.

Add a final check to compare the count with countThreshold and store the result in isAboveThreshold.

💡 Why This Matters

🌍 Real World

In real online stores or apps, quickly knowing the size of a collection helps with performance and user experience, especially when exact counts are slow.

💼 Career

Database developers and administrators often use estimatedDocumentCount() to optimize queries and monitor collection sizes efficiently.

1

Create the products collection with sample documents

Create a MongoDB collection called products and insert exactly these 5 documents: { name: "Laptop", price: 1200 }, { name: "Phone", price: 800 }, { name: "Tablet", price: 400 }, { name: "Monitor", price: 300 }, and { name: "Keyboard", price: 100 }.

MongoDB

// Insert the 5 specified product documents into the products collection
// Your code here

Need a hint?

Use insertMany on db.products with an array of 5 objects.

2

Add a countThreshold variable

Add a variable called countThreshold and set it to 3. This will be used later to check if the product count is above this number.

MongoDB

db.products.insertMany([
  { name: "Laptop", price: 1200 },
  { name: "Phone", price: 800 },
  { name: "Tablet", price: 400 },
  { name: "Monitor", price: 300 },
  { name: "Keyboard", price: 100 }
])

// Create a variable countThreshold and set it to 3
// Your code here

Need a hint?

Use const countThreshold = 3 to create the variable.

3

Use estimatedDocumentCount() to get the approximate count

Use estimatedDocumentCount() on the products collection and store the result in a variable called approxCount.

MongoDB

db.products.insertMany([
  { name: "Laptop", price: 1200 },
  { name: "Phone", price: 800 },
  { name: "Tablet", price: 400 },
  { name: "Monitor", price: 300 },
  { name: "Keyboard", price: 100 }
])

const countThreshold = 3;

// Use estimatedDocumentCount() on products and save to approxCount
// Your code here

Need a hint?

Call db.products.estimatedDocumentCount() and assign it to approxCount.

4

Compare count with threshold and store result

Create a variable called isAboveThreshold that is true if approxCount is greater than countThreshold, otherwise false.

MongoDB

db.products.insertMany([
  { name: "Laptop", price: 1200 },
  { name: "Phone", price: 800 },
  { name: "Tablet", price: 400 },
  { name: "Monitor", price: 300 },
  { name: "Keyboard", price: 100 }
])

const countThreshold = 3;

const approxCount = db.products.estimatedDocumentCount();

// Create isAboveThreshold to check if approxCount > countThreshold
// Your code here

Need a hint?

Use a comparison operator to set isAboveThreshold to true or false.