Write concern and data durability in MongoDB - Mini Project: Build & Apply

Understanding Write Concern and Data Durability in MongoDB

📖 Scenario: You are managing a small online store database using MongoDB. You want to make sure that when you add new orders, the data is safely saved and acknowledged properly to avoid losing any important information.

🎯 Goal: Build a MongoDB script that inserts order documents with different write concern levels to understand how data durability works.

📋 What You'll Learn

Create a MongoDB collection named orders with sample order documents.

Set a write concern variable to control acknowledgment level.

Insert a new order document using the specified write concern.

Add a final command to check the write concern settings applied.

💡 Why This Matters

🌍 Real World

In real-world applications, ensuring data is safely written to the database is critical to avoid data loss, especially in systems like online stores where orders must be reliably saved.

💼 Career

Understanding write concern and data durability is essential for database administrators and backend developers to configure MongoDB for reliable and consistent data storage.

1

Create the orders collection with sample data

Create a variable called orders that represents a MongoDB collection. Insert these exact documents into orders: { orderId: 1, item: "Book", quantity: 3 } and { orderId: 2, item: "Pen", quantity: 10 }.

MongoDB

// Create the orders collection and insert sample documents
// Your code here

Need a hint?

Use db.collection('orders') to get the collection. Use insertMany to add multiple documents.

2

Set the write concern variable

Create a variable called writeConcern and set it to an object with w: 1 to require acknowledgment from the primary server only.

MongoDB

const orders = db.collection('orders');
orders.insertMany([
  { orderId: 1, item: "Book", quantity: 3 },
  { orderId: 2, item: "Pen", quantity: 10 }
]);

// Set write concern to w: 1
// Your code here

Need a hint?

Write concern is an object with a w property. Use { w: 1 } for primary acknowledgment.

3

Insert a new order with the write concern

Use the insertOne method on orders to add this document: { orderId: 3, item: "Notebook", quantity: 5 }. Pass the writeConcern variable as the write concern option.

MongoDB

const orders = db.collection('orders');
orders.insertMany([
  { orderId: 1, item: "Book", quantity: 3 },
  { orderId: 2, item: "Pen", quantity: 10 }
]);

const writeConcern = { w: 1 };

// Insert new order with write concern
// Your code here

Need a hint?

Pass the write concern as an option object in the second argument of insertOne.

4

Check the write concern settings

Create a variable called currentWriteConcern and assign it the value of orders.writeConcern to check the current write concern settings of the collection.

MongoDB

const orders = db.collection('orders');
orders.insertMany([
  { orderId: 1, item: "Book", quantity: 3 },
  { orderId: 2, item: "Pen", quantity: 10 }
]);

const writeConcern = { w: 1 };

orders.insertOne(
  { orderId: 3, item: "Notebook", quantity: 5 },
  { writeConcern: writeConcern }
);

// Check current write concern
// Your code here

Need a hint?

Access the writeConcern property of the collection to see its settings.