Change stream events (insert, update, delete) in MongoDB - Mini Project: Build & Apply

Track Product Inventory Changes with MongoDB Change Streams

📖 Scenario: You manage a small store's product inventory using MongoDB. You want to watch for any changes to the products collection so you can react when products are added, updated, or removed.

🎯 Goal: Create a MongoDB change stream to listen for insert, update, and delete events on the products collection.

📋 What You'll Learn

Create a products collection with initial product documents.

Define a change stream pipeline to filter for insert, update, and delete events.

Open the change stream on the products collection using the pipeline.

Add a listener to handle and log the change events.

💡 Why This Matters

🌍 Real World

Change streams help businesses monitor live changes in their databases, such as inventory updates or user activity, enabling real-time reactions.

💼 Career

Understanding change streams is valuable for roles like database administrators, backend developers, and data engineers who build reactive and event-driven applications.

1

Create the products collection with initial data

Create a products collection and insert these exact documents: { _id: 1, name: "Pen", quantity: 100 }, { _id: 2, name: "Notebook", quantity: 200 }, and { _id: 3, name: "Eraser", quantity: 150 }.

MongoDB

// Insert initial products into the products collection
// Your code here

Need a hint?

Use db.products.insertMany() with an array of product objects.

2

Define a change stream pipeline to filter events

Create a variable called pipeline that filters change events to only include insert, update, and delete operations using { $match: { operationType: { $in: ["insert", "update", "delete"] } } }.

MongoDB

db.products.insertMany([
  { _id: 1, name: "Pen", quantity: 100 },
  { _id: 2, name: "Notebook", quantity: 200 },
  { _id: 3, name: "Eraser", quantity: 150 }
])

// Define the change stream pipeline to filter for insert, update, and delete events
// Your code here

Need a hint?

Use const pipeline = [{ $match: { operationType: { $in: ["insert", "update", "delete"] } } }].

3

Open the change stream on the products collection

Create a variable called changeStream that opens a change stream on db.products using the pipeline variable.

MongoDB

db.products.insertMany([
  { _id: 1, name: "Pen", quantity: 100 },
  { _id: 2, name: "Notebook", quantity: 200 },
  { _id: 3, name: "Eraser", quantity: 150 }
])

const pipeline = [
  { $match: { operationType: { $in: ["insert", "update", "delete"] } } }
]

// Open the change stream on the products collection using the pipeline
// Your code here

Need a hint?

Use const changeStream = db.products.watch(pipeline) to open the change stream.

4

Add a listener to handle and log change events

Use changeStream.on("change", (change) => { ... }) to add a listener that logs the change object to the console.

MongoDB

db.products.insertMany([
  { _id: 1, name: "Pen", quantity: 100 },
  { _id: 2, name: "Notebook", quantity: 200 },
  { _id: 3, name: "Eraser", quantity: 150 }
])

const pipeline = [
  { $match: { operationType: { $in: ["insert", "update", "delete"] } } }
]

const changeStream = db.products.watch(pipeline)

// Add a listener to the changeStream to log change events
// Your code here

Need a hint?

Use changeStream.on("change", (change) => { console.log("Change detected:", change) }).