API versioning for services in Microservices - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is API versioning in microservices?

API versioning is the practice of managing changes to an API by creating different versions. It helps services evolve without breaking existing clients.

beginner

Name two common ways to specify API versions.

1. URL path versioning (e.g., /v1/resource)
2. Header versioning (e.g., custom header like X-API-Version)

intermediate

Why is backward compatibility important in API versioning?

Backward compatibility ensures that older clients can still use the API without breaking when new versions are released.

intermediate

What is semantic versioning and how does it relate to API versioning?

Semantic versioning uses MAJOR.MINOR.PATCH format to indicate changes. Major changes break compatibility, minor add features, patch fixes bugs. It guides API version updates.

intermediate

Explain the difference between URL path versioning and header versioning.

URL path versioning includes the version in the URL making it visible and cache-friendly. Header versioning hides version info in headers, keeping URLs clean but harder to cache.

Which of the following is NOT a common API versioning method?

A Database schema versioning

B URL path versioning

C Query parameter versioning

D Header versioning

Database schema versioning is about database changes, not API versioning.

What does a major version change usually indicate in API versioning?

A Bug fixes only

B Breaking changes that may break clients

C No changes, just a label

D Backward-compatible feature additions

Major version changes usually mean breaking changes that can break existing clients.

Why might you choose header versioning over URL path versioning?

A To make version info visible in URLs

B Because headers are easier to cache

C To keep URLs clean and consistent

D Because it is the only supported method

Header versioning keeps URLs clean by hiding version info in headers.

What is a risk of not using API versioning?

A Clients may break when API changes

B API will be faster

C More secure API

D Easier to maintain

Without versioning, changes can break existing clients.

Which versioning method is easiest for caching proxies to handle?

A No versioning

B Header versioning

C Content negotiation

D URL path versioning

URL path versioning makes version part of the URL, which caching proxies can easily cache.

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

Think about visibility, caching, and client complexity.

Explain why API versioning is critical in microservices and how it supports service evolution.

Consider how many clients use the service and how often it changes.

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