Single document atomicity in MongoDB - Mini Project: Build & Apply

Understanding Single Document Atomicity in MongoDB

📖 Scenario: You are managing a small online store's inventory using MongoDB. You want to update the stock quantity and price of a product in a way that both changes happen together or not at all, ensuring data consistency.

🎯 Goal: Build a MongoDB update operation that modifies multiple fields of a single product document atomically.

📋 What You'll Learn

Create a collection named products with one product document having fields _id, name, stock, and price.

Define a variable product_id holding the _id of the product to update.

Write an update query that atomically changes the stock and price fields of the product with _id equal to product_id.

Ensure the update uses a single document atomic operation.

💡 Why This Matters

🌍 Real World

In real online stores, updating product stock and price together prevents errors like selling out-of-stock items or showing wrong prices.

💼 Career

Understanding single document atomicity is essential for database developers and backend engineers to maintain data consistency and reliability.

1

Create the products collection with one product document

Create a products collection and insert one document with _id set to 1, name set to 'Wireless Mouse', stock set to 50, and price set to 25.99.

MongoDB

// Insert the product document into the products collection
// Your code here

Need a hint?

Use insertOne to add a single document to the products collection.

2

Define the product_id variable

Define a variable called product_id and set it to 1 to represent the product's _id.

MongoDB

db.products.insertOne({ _id: 1, name: 'Wireless Mouse', stock: 50, price: 25.99 })
// Define product_id variable
// Your code here

Need a hint?

Use const product_id = 1 to store the product's ID.

3

Write an atomic update query for the product document

Write an update query using updateOne on the products collection that finds the document with _id equal to product_id and atomically updates the stock to 45 and price to 23.99.

MongoDB

db.products.insertOne({ _id: 1, name: 'Wireless Mouse', stock: 50, price: 25.99 })
const product_id = 1
// Update stock and price atomically
// Your code here

Need a hint?

Use updateOne with a filter on _id and the $set operator to update multiple fields atomically.

4

Complete the atomic update operation

Add the option {} to the updateOne method call to complete the update operation. This confirms the update is a single atomic operation on one document.

MongoDB

db.products.insertOne({ _id: 1, name: 'Wireless Mouse', stock: 50, price: 25.99 })
const product_id = 1
db.products.updateOne({ _id: product_id }, { $set: { stock: 45, price: 23.99 } })
// Add options object to updateOne
// Your code here

Need a hint?

Pass an empty options object {} as the third argument to updateOne to complete the call.