API versioning for services in Microservices - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Why use API versioning in microservices?

Which of the following is the main reason to implement API versioning in microservices?

A To improve the speed of the network between services

B To reduce the number of microservices in the system

C To allow clients to continue using old API features while new ones are added

D To encrypt the data sent between services

💡 Hint

Think about how changes in APIs affect existing clients.

API versioning allows backward compatibility so clients using older versions do not break when new features or changes are introduced.

❓ Architecture

intermediate

Common API versioning strategies

Which of the following is NOT a common strategy for API versioning in microservices?

A Header versioning (using custom headers)

B Database schema versioning

C URI versioning (e.g., /v1/resource)

D Query parameter versioning (e.g., ?version=1)

💡 Hint

Focus on how the API version is communicated to the client.

Database schema versioning is about data storage, not about how clients specify API versions. The other options are common ways to version APIs.

❓ scaling

advanced

Scaling challenges with multiple API versions

What is a major challenge when supporting multiple API versions in a microservices environment?

A Increased complexity in maintaining and deploying multiple versions simultaneously

B Elimination of the need for load balancers

C Automatic database migration for all versions

D Reduced network latency due to versioning

💡 Hint

Think about operational overhead when many versions run at once.

Supporting multiple API versions increases maintenance effort, testing, and deployment complexity because each version may require separate handling.

❓ tradeoff

advanced

Tradeoff of URI versioning vs Header versioning

Which statement best describes a tradeoff between URI versioning and Header versioning for APIs?

A URI versioning is easier for caching and routing, but Header versioning keeps URLs clean and RESTful

B Header versioning is easier for caching, but URI versioning hides the version from clients

C URI versioning requires clients to send custom headers, Header versioning uses URL paths

D Header versioning is deprecated and should never be used

💡 Hint

Consider how URLs and headers affect caching and readability.

URI versioning makes it simple for caches and routers to distinguish versions, but adds version info to URLs. Header versioning keeps URLs clean but can complicate caching.

❓ estimation

expert

Estimating storage impact of API versioning

A microservice stores user profiles and supports 3 API versions simultaneously. Each version stores 1MB of user data per 1000 users. If the service has 1 million users, approximately how much storage is needed to support all versions?

A 30 GB

B 3 TB

C 300 MB

D 3 GB

💡 Hint

Calculate storage per version, then multiply by number of versions.

1MB per 1000 users means 1000 MB (1 GB) per 1 million users per version. For 3 versions, total is 3 GB.

Practice

1. What is the main purpose of API versioning in microservices?

easy

A. To increase server hardware requirements

B. To improve database performance

C. To reduce network latency

D. To allow changes without breaking existing clients

Solution

1. Step 1: Understand API versioning goal

   API versioning is used to manage changes in APIs so that old clients still work without errors.

2. Step 2: Identify the main benefit

   This helps avoid breaking existing users when new features or fixes are added.

3. Final Answer:

   To allow changes without breaking existing clients -> Option D

4. Quick Check:

   API versioning = avoid breaking changes [OK]

Hint: API versioning prevents breaking old clients [OK]

Common Mistakes:

• Thinking it improves database speed
• Confusing it with network optimization
• Assuming it increases hardware needs

2. Which of the following is a common way to specify API version in a request?

easy

A. Using the URL path like /v1/resource

B. Embedding version in the database schema

C. Changing the server IP address

D. Using client-side cookies only

Solution

1. Step 1: Identify common API versioning methods

   API versions are often specified in the URL path, headers, or query parameters.

2. Step 2: Match the correct method

   Using the URL path like /v1/resource is a widely used and clear approach.

3. Final Answer:

   Using the URL path like /v1/resource -> Option A

4. Quick Check:

   URL path versioning = Using the URL path like /v1/resource [OK]

Hint: Version in URL path is common and clear [OK]

Common Mistakes:

• Confusing version with database schema
• Thinking server IP changes version
• Assuming cookies control API version

3. Given a microservice with two API versions running side by side, what happens when a client sends a request to /api/v2/users?

medium

A. The service processes the request using version 1 logic

B. The service returns an error because version 2 is unsupported

C. The service processes the request using version 2 logic

D. The service ignores the version and uses the latest version

Solution

1. Step 1: Understand version routing

   When multiple API versions run side by side, the version in the URL directs which logic to use.

2. Step 2: Match URL version to service logic

   A request to /api/v2/users should be handled by version 2 logic, not version 1 or latest by default.

3. Final Answer:

   The service processes the request using version 2 logic -> Option C

4. Quick Check:

   URL version directs logic = The service processes the request using version 2 logic [OK]

Hint: URL version selects matching service logic [OK]

Common Mistakes:

• Assuming version 1 logic runs always
• Thinking unsupported versions cause errors
• Believing latest version is default without version

4. A developer tries to version an API by changing the request header to X-API-Version: 3, but clients still get version 1 responses. What is the likely issue?

medium

A. The client is sending the wrong URL path

B. The service does not support header-based versioning

C. The server is down

D. The database schema is outdated

Solution

1. Step 1: Analyze versioning method mismatch

   If clients send version info in headers but the service expects URL path versioning, the header is ignored.

2. Step 2: Identify the cause of version mismatch

   The service likely does not support header-based versioning, so it defaults to version 1 responses.

3. Final Answer:

   The service does not support header-based versioning -> Option B

4. Quick Check:

   Unsupported header versioning = The service does not support header-based versioning [OK]

Hint: Check if service supports header versioning [OK]

Common Mistakes:

• Blaming wrong URL when header is used
• Assuming server down causes version mismatch
• Confusing database schema with API version

5. You need to design a microservice API that supports smooth migration from version 1 to version 2 without downtime. Which approach best supports this?

hard

A. Run both versions side by side and route requests based on URL version

B. Replace version 1 completely with version 2 immediately

C. Use only query parameters for versioning and ignore URL paths

D. Deploy version 2 on a different server without routing

Solution

1. Step 1: Understand smooth migration needs

   Smooth migration requires both versions to run simultaneously so clients can switch gradually.

2. Step 2: Choose routing strategy

   Routing requests based on URL version allows clients to specify which version they want, enabling coexistence.

3. Step 3: Evaluate other options

   Replacing immediately causes downtime; query-only versioning is less clear; separate servers without routing complicate access.

4. Final Answer:

   Run both versions side by side and route requests based on URL version -> Option A

5. Quick Check:

   Side-by-side versioning = Run both versions side by side and route requests based on URL version [OK]

Hint: Run versions side by side for smooth migration [OK]

Common Mistakes:

• Replacing old version immediately causing downtime
• Ignoring URL path versioning clarity
• Deploying without routing causing access issues