Why REST API best practices in HLD? - Purpose & Use Cases

The Big Idea

Discover how simple rules can transform chaotic APIs into smooth, reliable services everyone loves to use!

The Scenario

Imagine building a web service where every developer uses their own style for URLs, request methods, and responses. One developer uses GET for updates, another uses POST for fetching data, and error messages come in all shapes and sizes. Clients struggle to understand how to interact with the service, and bugs multiply.

The Problem

This manual, inconsistent approach causes confusion and slows down development. Clients waste time guessing how to use the API. Debugging becomes a nightmare because errors are unclear. Scaling the service is hard since there is no clear pattern to follow. Overall, it leads to frustration and wasted effort.

The Solution

REST API best practices provide a clear, consistent way to design APIs. They define how to use HTTP methods properly, structure URLs logically, handle errors uniformly, and document the API clearly. This makes APIs easy to understand, use, and maintain, reducing bugs and speeding up development.

Before vs After

✗ Before

POST /getUserData
Response: {"status": "ok", "data": {...}}

✓ After

GET /users/{id}
Response: 200 OK with user data JSON

What It Enables

Following REST API best practices enables smooth communication between clients and servers, making your service reliable, scalable, and easy to evolve.

Real Life Example

Think of a popular online store API where every product, order, and user has a clear URL, and clients know exactly how to create, read, update, or delete data without confusion. This consistency helps millions of users and developers interact seamlessly.

Key Takeaways

Manual API design leads to confusion and errors.

REST best practices bring clarity and consistency.

They make APIs easier to use, maintain, and scale.

Practice

1. Which HTTP method is typically used to update an existing resource in a REST API?

easy

A. PUT

B. GET

C. POST

D. DELETE

Solution

1. Step 1: Understand HTTP methods for REST

   GET retrieves data, POST creates new resources, PUT updates existing resources, DELETE removes resources.

2. Step 2: Identify method for updating

   PUT is the standard method to update or replace an existing resource in REST APIs.

3. Final Answer:

   PUT -> Option A

4. Quick Check:

   Update = PUT [OK]

Hint: Update resource? Think PUT method [OK]

Common Mistakes:

• Confusing POST with update instead of create
• Using GET for updates
• Using DELETE to update

2. Which of the following is the correct way to version a REST API in the URL?

easy

A. /v1/api/resource

B. /api/resource/v1

C. /api/v1/resource

D. /api/resource?version=1

Solution

1. Step 1: Understand common versioning patterns

   Versioning is often done in the URL path to clearly separate API versions.

2. Step 2: Identify correct version placement

   Placing version immediately after the base API path, like /api/v1/resource, is standard practice.

3. Final Answer:

   /api/v1/resource -> Option C

4. Quick Check:

   Version in path = /api/v1/ [OK]

Hint: Version goes right after /api/ in URL path [OK]

Common Mistakes:

• Putting version after resource name
• Using query parameters for versioning
• Placing version before /api/

3. Given the following API response status codes, which one indicates a successful resource creation?

{
  "status": 201,
  "message": "Created"
}

medium

A. 200 OK

B. 201 Created

C. 400 Bad Request

D. 404 Not Found

Solution

1. Step 1: Review HTTP status codes for success

   200 means success for general requests, 201 means resource created successfully.

2. Step 2: Match status code to creation

   201 Created is the correct code to indicate a new resource was successfully created.

3. Final Answer:

   201 Created -> Option B

4. Quick Check:

   Creation success = 201 [OK]

Hint: 201 means resource created successfully [OK]

Common Mistakes:

• Confusing 200 with creation success
• Using 400 or 404 for success
• Ignoring status code meaning

4. A developer designed a REST API endpoint as POST /users/delete to delete a user. What is the best fix to follow REST API best practices?

medium

A. Change to GET /users/delete

B. Keep POST /users/delete but add a query param

C. Use PUT /users/delete

D. Change to DELETE /users/{id}

Solution

1. Step 1: Identify correct HTTP method for deletion

   DELETE method is the standard for removing resources in REST APIs.

2. Step 2: Correct endpoint structure

   Use resource identifier in URL path like /users/{id} with DELETE method for clarity and REST compliance.

3. Final Answer:

   Change to DELETE /users/{id} -> Option D

4. Quick Check:

   Delete resource = DELETE /resource/{id} [OK]

Hint: Use DELETE method with resource ID in URL [OK]

Common Mistakes:

• Using POST for delete actions
• Using GET to delete resources
• Adding delete action in URL path

5. You want to design a REST API that returns a list of products with optional filtering by category and price range. Which approach follows REST API best practices?

hard

A. GET /products?category=electronics&min_price=100&max_price=500

B. POST /products/filter with JSON body containing filters

C. GET /products/filter/category/electronics/price/100-500

D. PUT /products with filter parameters in the body

Solution

1. Step 1: Understand filtering in REST APIs

   Filtering is best done using query parameters in GET requests to keep APIs simple and cacheable.

2. Step 2: Evaluate options for filtering

   GET /products?category=electronics&min_price=100&max_price=500 uses GET with query parameters, which is standard and clear. Other options misuse POST or PUT or complex URL paths.

3. Final Answer:

   GET /products?category=electronics&min_price=100&max_price=500 -> Option A

4. Quick Check:

   Filter with GET query params [OK]

Hint: Use GET with query parameters for filtering [OK]

Common Mistakes:

• Using POST or PUT for filtering
• Embedding filters in URL path segments
• Sending filters in request body for GET