API versioning strategies in HLD - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding URI Versioning

Which of the following best describes the main advantage of using URI versioning for APIs?

A It hides the API version from clients, reducing URL complexity.

B It allows clients to specify the API version in the URL, making it easy to cache and route requests.

C It automatically upgrades clients to the latest API version without changes.

D It uses HTTP headers to specify the version, keeping URLs clean.

💡 Hint

Think about how URLs are used in web requests and caching.

URI versioning places the version number in the URL path, which makes it explicit and easy for caching systems and routers to handle different versions separately.

❓ Architecture

intermediate

Choosing Header Versioning

What is a key benefit of using HTTP header versioning for APIs compared to URI versioning?

A It prevents caching of API responses.

B It forces clients to change URLs when switching versions.

C It keeps the URL clean and separates versioning concerns from resource identification.

D It makes it easier for browsers to bookmark specific API versions.

💡 Hint

Consider how URLs look and how headers work in HTTP.

Header versioning keeps the URL unchanged and uses HTTP headers to specify the version, which separates versioning from resource paths and keeps URLs clean.

❓ scaling

advanced

Scaling API with Multiple Versions

When supporting multiple API versions simultaneously, which strategy helps minimize server resource usage while maintaining backward compatibility?

A Implement a shared core logic with version-specific adapters to handle differences.

B Duplicate the entire codebase for each API version.

C Only support the latest version and reject older clients.

D Use URI versioning exclusively without shared components.

💡 Hint

Think about code reuse and maintenance effort.

Sharing core logic and using adapters for version differences reduces duplication and resource use while supporting multiple versions.

❓ tradeoff

advanced

Tradeoffs of Semantic Versioning in APIs

What is a major tradeoff when adopting semantic versioning (major.minor.patch) for API versioning?

A It forces clients to always use the latest patch version automatically.

B It simplifies client logic by hiding version details.

C It eliminates the need for backward compatibility.

D It provides detailed version info but can complicate client version negotiation.

💡 Hint

Consider how clients decide which version to use.

Semantic versioning gives detailed version info but requires clients to understand and negotiate versions carefully, adding complexity.

❓ estimation

expert

Estimating Storage for API Versioning Metadata

An API service stores metadata for each version of its endpoints. If each version adds 500KB of metadata and the service supports 12 versions with 100 endpoints each, approximately how much storage is needed for all metadata?

A 600 MB

B 600 KB

C 60 MB

D 6 GB

💡 Hint

Calculate total metadata size by multiplying versions, endpoints, and size per endpoint.

12 versions × 100 endpoints = 1200 endpoints total. 1200 × 500KB = 600,000 KB = 600 MB.

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