API versioning strategies in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is API versioning and why is it important?

API versioning is the practice of managing changes in an API by creating different versions. It is important to ensure backward compatibility and allow clients to continue using older versions without breaking when new features or fixes are added.

beginner

Name four common API versioning strategies.

Common API versioning strategies include: 1) URI versioning (version in URL path), 2) Query parameter versioning, 3) Header versioning (custom headers), 4) Content negotiation (Accept header).

beginner

What is URI versioning in APIs?

URI versioning means including the version number directly in the API URL path, for example, /api/v1/resource. It is simple and easy to cache but can lead to duplicated endpoints.

intermediate

Explain header versioning and one advantage it has.

Header versioning uses custom HTTP headers to specify the API version, such as 'X-API-Version: 1'. An advantage is that it keeps URLs clean and separates versioning from resource paths.

intermediate

What is content negotiation in API versioning?

Content negotiation uses the HTTP Accept header to specify the version, for example, 'Accept: application/vnd.example.v1+json'. It allows flexible versioning and supports multiple formats but can be complex to implement.

Which API versioning strategy includes the version number in the URL path?

A URI versioning

B Header versioning

C Query parameter versioning

D Content negotiation

URI versioning places the version directly in the URL path, such as /api/v1/resource.

What is a key benefit of using header versioning?

A Easy to bookmark URLs

B Simplifies caching

C Keeps URLs clean

D Automatically supported by browsers

Header versioning keeps URLs clean by moving version info to HTTP headers.

Which versioning method uses the Accept HTTP header?

A Content negotiation

B URI versioning

C Query parameter versioning

D Header versioning

Content negotiation uses the Accept header to specify API version and format.

What is a disadvantage of URI versioning?

A Hard to cache

B Leads to duplicated endpoints

C Requires custom headers

D Not supported by HTTP

URI versioning can lead to duplicated endpoints for each version.

Which versioning strategy can be added without changing the URL?

A URI versioning

B Path suffix versioning

C Query parameter versioning

D Header versioning

Header versioning adds version info in HTTP headers, leaving URLs unchanged.

Describe the main API versioning strategies and their pros and cons.

Think about how version info is passed and how it affects URLs and clients.

Explain why API versioning is necessary and how it helps maintain backward compatibility.

Consider what happens when APIs change and clients still use old versions.

Practice

1. Which of the following is a common method to implement API versioning?

easy

A. Changing the database schema without notice

B. Including the version number in the URL path

C. Using random query parameters unrelated to version

D. Ignoring backward compatibility

Solution

1. Step 1: Understand common API versioning methods

   API versioning often uses clear, explicit methods like URL paths, query parameters, or headers to indicate version.

2. Step 2: Evaluate options for correctness

   Only including the version number in the URL path is a standard, clear method. Other options either break compatibility or are unrelated.

3. Final Answer:

   Including the version number in the URL path -> Option B

4. Quick Check:

   Version in URL path = B [OK]

Hint: Version in URL path is the most visible method [OK]

Common Mistakes:

• Confusing random query parameters with versioning
• Ignoring backward compatibility importance
• Assuming database changes equal API versioning

2. Which syntax correctly shows versioning using a query parameter in an API request?

easy

A. GET /api/resource?v=2

B. GET /api/v2/resource

C. GET /api/resource/version2

D. GET /api/resource?version-2

Solution

1. Step 1: Identify query parameter versioning syntax

   Query parameter versioning appends a key-value pair like ?v=2 to the URL.

2. Step 2: Compare options for correct query parameter format

   GET /api/resource?v=2 uses ?v=2 which is correct. Others use path or invalid query syntax.

3. Final Answer:

   GET /api/resource?v=2 -> Option A

4. Quick Check:

   Query param version = C [OK]

Hint: Query params use ?key=value format [OK]

Common Mistakes:

• Using path segments instead of query parameters
• Incorrect query parameter syntax like missing '='
• Confusing version in path with query versioning

3. Given this API Gateway routing rule: if request.header['API-Version'] == 'v2' then route to service_v2 else route to service_v1, what happens when a request has no API-Version header?

medium

A. Request is rejected with error

B. Request is routed to service_v2

C. Request is routed to service_v1

D. Request is routed randomly

Solution

1. Step 1: Analyze the routing condition

   The rule routes to service_v2 only if header 'API-Version' equals 'v2'. Otherwise, it routes to service_v1.

2. Step 2: Determine routing when header is missing

   If the header is missing, condition fails, so request goes to service_v1 by default.

3. Final Answer:

   Request is routed to service_v1 -> Option C

4. Quick Check:

   Missing header defaults to v1 routing = A [OK]

Hint: Missing header triggers else branch routing [OK]

Common Mistakes:

• Assuming missing header routes to v2
• Thinking missing header causes error
• Believing routing is random without header

4. A developer implemented API versioning by adding a new version in the URL path but forgot to update the API Gateway routing rules. What is the most likely problem?

medium

A. The old version will be disabled automatically

B. All requests will be routed correctly to the new version

C. API Gateway will automatically detect and route new versions

D. Requests to the new version will fail or go to the old service

Solution

1. Step 1: Understand API Gateway role in version routing

   API Gateway must be configured to route requests to correct service versions based on URL or headers.

2. Step 2: Analyze impact of missing routing update

   If routing rules are not updated for new URL version, requests won't reach the new service and may fail or default to old service.

3. Final Answer:

   Requests to the new version will fail or go to the old service -> Option D

4. Quick Check:

   Missing routing update causes failures = A [OK]

Hint: Update routing rules with new version URLs [OK]

Common Mistakes:

• Assuming API Gateway auto-updates routing
• Believing old version disables automatically
• Ignoring routing configuration importance

5. You need to design an API that supports multiple versions simultaneously without breaking existing clients. Which strategy best supports this requirement?

hard

A. Use an API Gateway to route requests based on version in headers or URL

B. Change the API contract directly and remove old versions immediately

C. Use only query parameters for versioning and ignore headers

D. Deploy a single service that handles all versions internally without routing

Solution

1. Step 1: Identify requirements for supporting multiple versions

   Supporting multiple versions simultaneously requires clear routing to different service versions without breaking clients.

2. Step 2: Evaluate strategies for version management

   Using an API Gateway to route requests based on version in headers or URL cleanly separates versions and maintains backward compatibility.

3. Step 3: Eliminate less scalable or risky options

   Removing old versions immediately breaks clients; relying only on query parameters limits flexibility; single service handling all versions complicates code and risks errors.

4. Final Answer:

   Use an API Gateway to route requests based on version in headers or URL -> Option A

5. Quick Check:

   API Gateway routing supports multiple versions = D [OK]

Hint: API Gateway routing is key for multi-version support [OK]

Common Mistakes:

• Removing old versions too soon
• Ignoring header-based versioning
• Overloading single service with all versions