REST constraints and principles in Rest API - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Which REST constraint ensures stateless communication?

In REST architecture, which constraint requires that each request from client to server must contain all the information needed to understand and process the request?

A Cacheable

B Stateless

C Client-Server

D Layered System

💡 Hint

Think about how the server treats each request independently.

The Stateless constraint means the server does not store any client context between requests. Each request must be self-contained.

❓ Predict Output

intermediate

What is the HTTP method used to update a resource completely in REST?

Given the REST principles, which HTTP method is typically used to replace an entire resource with new data?

A PUT

B POST

C GET

D PATCH

💡 Hint

This method replaces the entire resource, not just parts of it.

The PUT method is used to update or replace a resource completely. PATCH is for partial updates.

❓ Predict Output

advanced

What is the expected response status code after a successful DELETE request in REST?

After successfully deleting a resource using RESTful API, what HTTP status code should the server return?

A 404 Not Found

B 201 Created

C 200 OK

D 204 No Content

💡 Hint

The server confirms success but sends no content back.

204 No Content means the request was successful but there is no content to return, which is typical after a DELETE.

🧠 Conceptual

advanced

Which REST constraint improves scalability by enabling intermediaries to cache responses?

Which REST architectural constraint allows responses to be labeled as cacheable or non-cacheable to improve network efficiency and scalability?

A Uniform Interface

B Code on Demand

C Cacheable

D Stateless

💡 Hint

Think about how browsers and proxies store responses to reduce server load.

The Cacheable constraint allows responses to be stored and reused, reducing server load and improving performance.

🧠 Conceptual

expert

What principle does REST follow to separate client and server concerns?

Which REST constraint enforces a separation of concerns by keeping the user interface concerns separate from data storage concerns?

A Client-Server

B Stateless

C Layered System

D Uniform Interface

💡 Hint

This principle allows independent evolution of client and server.

The Client-Server constraint separates the user interface from data storage, allowing each to evolve independently.

Practice

1. Which of the following is a key constraint of REST that ensures each request from client to server must contain all the information needed to understand and process the request?

easy

A. Cacheability

B. Layered System

C. Statelessness

D. Code on Demand

Solution

1. Step 1: Understand the meaning of statelessness in REST

   Statelessness means the server does not store any client context between requests. Each request must be self-contained.

2. Step 2: Match the constraint to the description

   The description says each request must have all needed info, which matches statelessness.

3. Final Answer:

   Statelessness -> Option C

4. Quick Check:

   Request self-contained = Statelessness [OK]

Hint: Requests must be independent and self-contained [OK]

Common Mistakes:

• Confusing cacheability with statelessness
• Thinking layered system means stateless
• Assuming code on demand is required

2. Which HTTP method is NOT considered safe and idempotent according to REST principles?

easy

A. POST

B. PUT

C. GET

D. DELETE

Solution

1. Step 1: Recall safe and idempotent HTTP methods

   GET, PUT, and DELETE are idempotent; GET is safe. POST is neither safe nor idempotent.

2. Step 2: Identify the method that is not safe and idempotent

   POST changes server state and can create multiple resources, so it is not idempotent or safe.

3. Final Answer:

   POST -> Option A

4. Quick Check:

   POST is not safe or idempotent [OK]

Hint: POST changes data and is not idempotent [OK]

Common Mistakes:

• Thinking PUT is unsafe
• Confusing DELETE as unsafe
• Assuming GET modifies data

3. Given the following REST API response headers, which constraint is being applied?

Cache-Control: max-age=3600
ETag: "abc123"

medium

A. Cacheability

B. Uniform Interface

C. Statelessness

D. Client-Server

Solution

1. Step 1: Analyze the headers Cache-Control and ETag

   Cache-Control and ETag headers control how responses are cached by clients or intermediaries.

2. Step 2: Identify the REST constraint related to caching

   Cacheability means responses can be stored and reused to improve performance.

3. Final Answer:

   Cacheability -> Option A

4. Quick Check:

   Cache headers = Cacheability [OK]

Hint: Cache headers indicate cacheability constraint [OK]

Common Mistakes:

• Confusing cache headers with statelessness
• Thinking uniform interface relates to headers
• Assuming client-server means caching

4. You have a REST API that stores user sessions on the server between requests. Which REST constraint is violated and how can you fix it?

medium

A. Uniform Interface; change URL structure

B. Cacheability; disable caching on responses

C. Layered System; remove intermediaries

D. Statelessness; move session data to client or include in each request

Solution

1. Step 1: Identify the violated constraint

   Storing session data on server between requests breaks statelessness because server keeps client state.

2. Step 2: Suggest a fix to restore statelessness

   Move session info to client (like tokens) or send all needed info in each request.

3. Final Answer:

   Statelessness; move session data to client or include in each request -> Option D

4. Quick Check:

   Server session storage breaks statelessness [OK]

Hint: No server session storage means statelessness [OK]

Common Mistakes:

• Confusing cacheability with session storage
• Thinking layered system relates to sessions
• Trying to fix by changing URLs

5. You want to design a REST API that allows clients to update user profiles partially without sending the entire profile data. Which HTTP method and REST principle best support this requirement?

hard

A. PUT method and Uniform Interface constraint

B. PATCH method and Uniform Interface constraint

C. POST method and Statelessness constraint

D. DELETE method and Cacheability constraint

Solution

1. Step 1: Identify the HTTP method for partial updates

   PATCH is designed for partial updates, unlike PUT which replaces entire resource.

2. Step 2: Connect the method to the REST principle

   Uniform Interface means using standard methods consistently; PATCH fits this principle for partial updates.

3. Final Answer:

   PATCH method and Uniform Interface constraint -> Option B

4. Quick Check:

   Partial update = PATCH + Uniform Interface [OK]

Hint: Partial update uses PATCH and uniform interface [OK]

Common Mistakes:

• Using PUT for partial updates
• Confusing POST with PATCH
• Linking DELETE to updates