REST API design for systems in HLD - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does REST stand for in REST API?

REST stands for Representational State Transfer. It is an architectural style for designing networked applications.

beginner

Why should REST APIs use nouns in their endpoint URLs instead of verbs?

REST APIs use nouns to represent resources because HTTP methods (GET, POST, PUT, DELETE) define the action. This keeps URLs simple and consistent.

intermediate

What HTTP method is typically used to update an existing resource in REST API?

The PUT method is typically used to update an existing resource completely, while PATCH is used for partial updates.

beginner

What is the purpose of status codes in REST API responses?

Status codes tell the client if the request was successful or if there was an error, and what type of error occurred. For example, 200 means success, 404 means resource not found.

intermediate

How can REST APIs handle versioning to maintain backward compatibility?

Versioning can be handled by including the version number in the URL path (e.g., /v1/resource) or in request headers. This allows clients to use different API versions without breaking.

Which HTTP method is used to retrieve data from a REST API?

A POST

B PUT

C GET

D DELETE

GET is used to retrieve data without changing the resource.

In REST API design, what should the URL /users/123 represent?

A A list of all users

B A specific user resource with ID 123

C An action to update user 123

D A login endpoint

URLs represent resources, so /users/123 points to the user with ID 123.

What status code indicates that a resource was not found?

A 404

B 201

C 200

D 500

404 means the requested resource does not exist.

Which HTTP method is best for creating a new resource?

A DELETE

B GET

C PUT

D POST

POST is used to create new resources.

How can you version a REST API to avoid breaking existing clients?

A Include version number in URL or headers

B Avoid using HTTP status codes

C Use only POST method

D Change URLs randomly

Including version info in URLs or headers helps maintain backward compatibility.

Explain the key principles of REST API design and why they matter.

Think about how REST APIs organize resources and communicate actions.

Describe how you would design a REST API endpoint for managing books in a library system.

Focus on resource naming and HTTP methods.

Practice

1. Which HTTP method is typically used to retrieve data from a REST API without modifying it?

easy

A. DELETE

B. POST

C. GET

D. PUT

Solution

1. Step 1: Understand HTTP methods in REST

   GET is used to request data without changing the server state.

2. Step 2: Match method to action

   POST creates or modifies data, PUT updates, DELETE removes data.

3. Final Answer:

   GET -> Option C

4. Quick Check:

   Retrieve data = GET [OK]

Hint: GET is for reading data only, no changes [OK]

Common Mistakes:

• Confusing POST with GET
• Using PUT for data retrieval
• Thinking DELETE retrieves data

2. Which of the following is the correct URL format to access a specific user with ID 123 in a REST API?

easy

A. /users/123

B. /users/getUser?id=123

C. /getUser/123

D. /users?id=123

Solution

1. Step 1: Identify RESTful URL design

   REST URLs use resource names and IDs as path segments, not actions or query for specific resource.

2. Step 2: Compare options

   /users/123 correctly points to user resource with ID 123; others use verbs or query parameters incorrectly.

3. Final Answer:

   /users/123 -> Option A

4. Quick Check:

   Resource ID in path = /users/123 [OK]

Hint: Use resource path + ID, avoid verbs in URL [OK]

Common Mistakes:

• Using verbs like getUser in URL
• Using query params for resource ID
• Mixing action names with resource paths

3. Given the following REST API call: DELETE /orders/456, what is the expected outcome?

medium

A. It deletes order 456 from the system

B. It updates order 456's status

C. It retrieves order 456's details

D. It creates a new order with ID 456

Solution

1. Step 1: Understand HTTP DELETE method

   DELETE is used to remove a resource identified by the URL.

2. Step 2: Analyze the URL and method

   /orders/456 points to order with ID 456; DELETE removes it.

3. Final Answer:

   It deletes order 456 from the system -> Option A

4. Quick Check:

   DELETE + resource ID = delete resource [OK]

Hint: DELETE method removes resource at given URL [OK]

Common Mistakes:

• Thinking DELETE retrieves data
• Confusing DELETE with POST
• Assuming DELETE creates or updates

4. A developer designed a REST API endpoint as POST /users/123/updateEmail to update a user's email. What is the main issue with this design?

medium

A. Using POST instead of GET for update

B. Including action 'updateEmail' in the URL violates REST principles

C. Missing user ID in the URL

D. Using query parameters instead of path variables

Solution

1. Step 1: Review REST URL design principles

   REST APIs should use resource paths, not actions in URLs.

2. Step 2: Identify the problem in the URL

   Including 'updateEmail' is an action, which breaks REST design; updates should use PUT or PATCH on /users/123.

3. Final Answer:

   Including action 'updateEmail' in the URL violates REST principles -> Option B

4. Quick Check:

   URLs represent resources, not actions [OK]

Hint: Avoid verbs in URLs; use HTTP methods for actions [OK]

Common Mistakes:

• Using verbs in URL paths
• Confusing POST with GET for updates
• Omitting resource IDs

5. You need to design a REST API for a system managing books and their authors. Which design best follows REST principles for retrieving all books by a specific author with ID 789?

hard

A. /books/authors/789

B. /books?author=789

C. /getBooksByAuthor/789

D. /authors/789/books

Solution

1. Step 1: Understand resource hierarchy in REST

   Authors and books are resources; books by an author are a sub-resource of author.

2. Step 2: Evaluate URL options

   /authors/789/books clearly shows books belonging to author 789, following REST resource nesting.

3. Step 3: Consider query vs path

   While query parameters can filter, nested resource path is more RESTful for related resources.

4. Final Answer:

   /authors/789/books -> Option D

5. Quick Check:

   Nested resource path shows relationship [OK]

Hint: Use nested paths for related resources [OK]

Common Mistakes:

• Using verbs in URL
• Overusing query parameters
• Ignoring resource relationships