Why versioning prevents breaking changes in Rest API - See It in Action

Why Versioning Prevents Breaking Changes in REST APIs

📖 Scenario: You are building a simple REST API for a bookstore. The API returns book details to users. Over time, you want to add new features without breaking existing clients that use your API.

🎯 Goal: Learn how to use API versioning to prevent breaking changes by creating two versions of a simple API response.

📋 What You'll Learn

Create a dictionary called book_v1 with keys title and author and their exact values

Create a variable called api_version and set it to the string 'v1'

Use an if statement to select the correct book dictionary based on api_version

Print the selected book dictionary

💡 Why This Matters

🌍 Real World

APIs often change over time. Versioning lets developers add new features without breaking apps that use old versions.

💼 Career

Understanding API versioning is important for backend developers and anyone working with web services to maintain compatibility.

1

Create the initial book data for version 1

Create a dictionary called book_v1 with these exact entries: 'title': 'The Great Gatsby' and 'author': 'F. Scott Fitzgerald'

Rest API

# Create the book_v1 dictionary with title and author
# Your code here

Hint

Use curly braces {} to create a dictionary with the keys and values exactly as shown.

2

Set the API version variable

Create a variable called api_version and set it to the string 'v1'

Rest API

book_v1 = {'title': 'The Great Gatsby', 'author': 'F. Scott Fitzgerald'}
# Set the api_version variable to 'v1'
# Your code here

Hint

Use quotes around v1 to make it a string.

3

Add version 2 book data and select based on version

Create a dictionary called book_v2 with keys title, author, and year with values 'The Great Gatsby', 'F. Scott Fitzgerald', and 1925 respectively. Then use an if statement to create a variable book that is book_v1 if api_version is 'v1', else book_v2.

Rest API

book_v1 = {'title': 'The Great Gatsby', 'author': 'F. Scott Fitzgerald'}
api_version = 'v1'
# Create book_v2 dictionary with title, author, and year
# Use if statement to assign book based on api_version
# Your code here

Hint

Remember to use if api_version == 'v1' to check the version and assign book accordingly.

4

Print the selected book data

Write a print statement to display the variable book

Rest API

book_v1 = {'title': 'The Great Gatsby', 'author': 'F. Scott Fitzgerald'}
api_version = 'v1'
book_v2 = {'title': 'The Great Gatsby', 'author': 'F. Scott Fitzgerald', 'year': 1925}
if api_version == 'v1':
    book = book_v1
else:
    book = book_v2
# Print the book dictionary
# Your code here

Hint

Use print(book) to show the selected book data.

Practice

1. Why is versioning important in REST APIs?

easy

A. It makes the API run faster.

B. It reduces the number of API endpoints.

C. It allows clients to use old API features without breaking when new changes happen.

D. It automatically fixes bugs in the API.

Solution

1. Step 1: Understand the role of versioning

   Versioning separates different stages of an API so changes don't break existing clients.

2. Step 2: Identify the benefit for clients

   Clients can keep using the old API version safely while new versions add features or fix bugs.

3. Final Answer:

   It allows clients to use old API features without breaking when new changes happen. -> Option C

4. Quick Check:

   Versioning prevents breaking changes = B [OK]

Hint: Versioning keeps old and new APIs separate to avoid breakage [OK]

Common Mistakes:

• Thinking versioning speeds up the API
• Believing versioning reduces endpoints
• Assuming versioning fixes bugs automatically

2. Which of the following is a correct way to include versioning in a REST API URL?

easy

A. /api/users/v1

B. /api/v1/users

C. /v1api/users

D. /api/users?version=1

Solution

1. Step 1: Identify common versioning URL patterns

   Versioning is usually done by adding a version segment like /v1/ after the base API path.

2. Step 2: Check each option

   /api/v1/users uses /api/v1/users which is the standard and clear way to version APIs.

3. Final Answer:

   /api/v1/users -> Option B

4. Quick Check:

   Version in URL path = A [OK]

Hint: Version usually appears as /v1/ in the API path [OK]

Common Mistakes:

• Putting version after resource name
• Combining version and resource without slash
• Using query parameters for versioning (less common)

3. Given this API change: adding a new required field to the user creation endpoint without versioning, what is the likely result for existing clients?

medium

A. The API will automatically update clients to send the new field.

B. Existing clients will continue working without any issues.

C. The API will ignore the missing field and use a default silently.

D. Existing clients will break because they don't send the new required field.

Solution

1. Step 1: Understand impact of adding required fields without versioning

   Adding a required field means clients must send it or the API rejects the request.

2. Step 2: Predict behavior for old clients

   Old clients don't send the new field, so their requests fail, causing breakage.

3. Final Answer:

   Existing clients will break because they don't send the new required field. -> Option D

4. Quick Check:

   Adding required field breaks old clients = D [OK]

Hint: New required fields break old clients without versioning [OK]

Common Mistakes:

• Assuming API auto-fills missing required fields
• Thinking old clients keep working unchanged
• Believing API updates clients automatically

4. You have an API with versioning: /api/v1/users and /api/v2/users. You accidentally remove a field in v2 that clients still use in v1. What is the best fix?

medium

A. Keep the field in v1 and remove only in v2 to avoid breaking v1 clients.

B. Remove the field from both versions immediately.

C. Remove the field from v1 and v2 but notify clients to update.

D. Merge v1 and v2 into a single version without the field.

Solution

1. Step 1: Understand versioning purpose

   Versioning allows old clients to keep using old API features safely.

2. Step 2: Apply versioning to field removal

   Removing a field only in v2 keeps v1 stable for clients still using it.

3. Final Answer:

   Keep the field in v1 and remove only in v2 to avoid breaking v1 clients. -> Option A

4. Quick Check:

   Remove features only in new versions = A [OK]

Hint: Remove features only in new versions, keep old stable [OK]

Common Mistakes:

• Removing fields from all versions at once
• Merging versions and breaking old clients
• Ignoring impact on old clients

5. You want to add a new optional feature to your API without breaking existing clients. Which versioning strategy best supports this?

hard

A. Create a new version (e.g., /api/v2) with the feature, keep /api/v1 unchanged.

B. Add the feature directly to /api/v1 and remove old features.

C. Change the API URL to /api/users without version and add the feature.

D. Force all clients to update to the new feature immediately.

Solution

1. Step 1: Identify safe way to add features

   Adding a new version keeps old clients working and adds new features safely.

2. Step 2: Evaluate options

   Create a new version (e.g., /api/v2) with the feature, keep /api/v1 unchanged. creates /api/v2 with new feature and keeps /api/v1 stable, preventing breakage.

3. Final Answer:

   Create a new version (e.g., /api/v2) with the feature, keep /api/v1 unchanged. -> Option A

4. Quick Check:

   New version for new features = C [OK]

Hint: Add features in new versions, keep old stable [OK]

Common Mistakes:

• Changing old versions directly
• Removing old features immediately
• Not using versioning at all