Batch update patterns in Rest API - Mini Project: Build & Apply

Batch Update Patterns with REST API

📖 Scenario: You are building a simple REST API for a bookstore. The store wants to update the prices of multiple books at once to run a sale.Batch updates let you change many items in one request, saving time and effort.

🎯 Goal: Create a batch update endpoint that accepts a list of book IDs and new prices, then updates the prices in the data store.

📋 What You'll Learn

Create a data structure to hold books with their IDs and prices

Add a configuration variable for the discount percentage

Write the batch update logic to apply the discount to selected books

Print the updated books after the batch update

💡 Why This Matters

🌍 Real World

Batch updates are common in online stores to quickly change prices or stock for many products at once.

💼 Career

Understanding batch update patterns helps backend developers build efficient APIs that handle multiple changes in one request.

1

DATA SETUP: Create the initial books data

Create a dictionary called books with these exact entries: 1: {'title': 'Book A', 'price': 100}, 2: {'title': 'Book B', 'price': 150}, 3: {'title': 'Book C', 'price': 200}

Rest API

# Create the books dictionary with IDs and prices
# Your code here

Hint

Use a dictionary with keys as book IDs and values as dictionaries holding title and price.

2

CONFIGURATION: Set the discount percentage

Create a variable called discount_percent and set it to 10 to represent a 10% discount

Rest API

books = {
    1: {'title': 'Book A', 'price': 100},
    2: {'title': 'Book B', 'price': 150},
    3: {'title': 'Book C', 'price': 200}
}
# Set the discount_percent variable
# Your code here

Hint

Just create a variable with the exact name and value.

3

CORE LOGIC: Apply batch update to selected books

Write a function called batch_update_prices that takes book_ids (a list) and updates each book's price in books by reducing it by discount_percent. Use a for loop with book_id to iterate over book_ids and update the price inside the function.

Rest API

books = {
    1: {'title': 'Book A', 'price': 100},
    2: {'title': 'Book B', 'price': 150},
    3: {'title': 'Book C', 'price': 200}
}
discount_percent = 10

# Define batch_update_prices function below
# Your code here

Hint

Use a function with a for loop to update prices by applying the discount.

4

OUTPUT: Run batch update and print updated books

Call batch_update_prices with the list [1, 3] and then print the books dictionary to show updated prices

Rest API

books = {
    1: {'title': 'Book A', 'price': 100},
    2: {'title': 'Book B', 'price': 150},
    3: {'title': 'Book C', 'price': 200}
}
discount_percent = 10

def batch_update_prices(book_ids):
    for book_id in book_ids:
        if book_id in books:
            old_price = books[book_id]['price']
            new_price = old_price * (100 - discount_percent) / 100
            books[book_id]['price'] = round(new_price, 2)

# Call batch_update_prices and print books
# Your code here

Hint

Call the function with the list [1, 3] and print the books dictionary.

Practice

1. What is the main advantage of using batch update patterns in REST APIs?

easy

A. They only work with GET requests.

B. They allow updating multiple items with a single request, saving time.

C. They require sending separate requests for each item.

D. They increase the number of requests to the server.

Solution

1. Step 1: Understand batch update purpose

   Batch update patterns let you update many items at once instead of one by one.

2. Step 2: Identify the benefit

   This reduces the number of requests and saves time and server resources.

3. Final Answer:

   They allow updating multiple items with a single request, saving time. -> Option B

4. Quick Check:

   Batch update = single request for many items [OK]

Hint: Batch updates reduce requests by combining many updates [OK]

Common Mistakes:

• Thinking batch updates increase requests
• Confusing batch update with single item update
• Assuming batch updates use GET method

2. Which HTTP method is most appropriate for batch updates in REST APIs?

easy

A. GET

B. POST

C. PATCH

D. DELETE

Solution

1. Step 1: Recall HTTP methods for updates

   PATCH is used to partially update resources, suitable for batch updates.

2. Step 2: Eliminate other methods

   GET retrieves data, POST creates new data, DELETE removes data, so they are not best for batch updates.

3. Final Answer:

   PATCH -> Option C

4. Quick Check:

   Batch update uses PATCH method [OK]

Hint: Use PATCH for partial or batch updates [OK]

Common Mistakes:

• Using GET for updates
• Confusing POST with update method
• Using DELETE instead of PATCH

3. Given this JSON payload sent in a PATCH request for batch update:

[{"id":1,"status":"done"},{"id":2,"status":"pending"}]

What does this payload represent?

medium

A. Retrieve items with id 1 and 2.

B. Create two new items with given ids and statuses.

C. Delete items with id 1 and 2.

D. Update status of items with id 1 and 2 to 'done' and 'pending' respectively.

Solution

1. Step 1: Analyze JSON payload

   The payload is an array of objects each with 'id' and 'status' fields, indicating updates.

2. Step 2: Understand PATCH semantics

   PATCH updates existing items partially, so this changes status fields for items with id 1 and 2.

3. Final Answer:

   Update status of items with id 1 and 2 to 'done' and 'pending' respectively. -> Option D

4. Quick Check:

   PATCH with array updates multiple items [OK]

Hint: PATCH with array updates multiple items by id [OK]

Common Mistakes:

• Thinking PATCH creates new items
• Confusing update with delete
• Assuming it retrieves data

4. You send this PATCH request payload to update multiple items:

[{"id":1,"status":"done"}, {"status":"pending"}]

What is the likely problem?

medium

A. Missing 'id' in second object causes update failure or error.

B. The payload is valid and will update all items.

C. Using PATCH instead of POST causes syntax error.

D. The array should be empty for batch updates.

Solution

1. Step 1: Check each object in payload

   The second object lacks 'id', so the server cannot identify which item to update.

2. Step 2: Understand update requirements

   Each update must specify the item to update, usually by 'id'. Missing it causes failure or error.

3. Final Answer:

   Missing 'id' in second object causes update failure or error. -> Option A

4. Quick Check:

   Each update needs an identifier like 'id' [OK]

Hint: Every update object must include an identifier like 'id' [OK]

Common Mistakes:

• Assuming missing 'id' is allowed
• Confusing PATCH with POST errors
• Thinking empty arrays are required

5. You want to batch update user roles but only for users currently active. Which pattern best fits this requirement?

hard

A. Send a PATCH request with an array of user objects filtered to active users only.

B. Send separate PATCH requests for all users regardless of status.

C. Use GET request to update roles for active users.

D. Send a DELETE request with active users to update roles.

Solution

1. Step 1: Identify filtering need

   Only active users should be updated, so filter users before sending batch update.

2. Step 2: Choose correct method and payload

   PATCH with an array of filtered user objects updates roles efficiently in one request.

3. Final Answer:

   Send a PATCH request with an array of user objects filtered to active users only. -> Option A

4. Quick Check:

   Filter then batch update with PATCH [OK]

Hint: Filter data first, then batch update with PATCH [OK]

Common Mistakes:

• Sending updates for all users without filtering
• Using GET or DELETE for updates
• Sending multiple separate requests instead of batch