HTTP Methods Interview Questions and Answers

Master HTTP Methods with the top 15 interview questions and answers. Learn GET, POST, PUT, PATCH, DELETE, HEAD, OPTIONS, idempotency, safety, production use cases, Spring Boot examples, common mistakes, and REST API best practices.

Introduction

HTTP Methods (also known as HTTP Verbs) define the action a client wants to perform on a resource. They are one of the most fundamental concepts in REST API development and are frequently asked in Java, Spring Boot, Microservices, and System Design interviews.

Choosing the correct HTTP method makes APIs predictable, scalable, and compliant with REST principles. Interviewers often ask candidates to explain the difference between GET vs POST, PUT vs PATCH, safe vs idempotent methods, and how HTTP methods are used in production systems.

In this guide, you'll learn the 15 most important HTTP Methods interview questions with production-ready explanations, Spring Boot examples, diagrams, best practices, common mistakes, and interview follow-up questions.

What You'll Learn

After completing this guide, you'll be able to:

Understand every major HTTP method.
Explain when to use GET, POST, PUT, PATCH, DELETE, HEAD, and OPTIONS.
Differentiate Safe and Idempotent methods.
Design production-ready REST APIs.
Answer enterprise-level REST interview questions confidently.

HTTP Methods Overview

                 HTTP Methods

                    Client
                       │
             HTTP Request (Method)
                       │
        ┌──────────────┼──────────────┐
        ▼              ▼              ▼
      GET            POST            PUT
    Retrieve        Create        Replace
        │              │              │
        ▼              ▼              ▼
     PATCH          DELETE        OPTIONS
 Partial Update     Remove      Discover

1. What are HTTP Methods?

Short Answer

HTTP Methods define the type of operation a client wants to perform on a resource.

Common HTTP Methods

Method	Operation
GET	Retrieve Resource
POST	Create Resource
PUT	Replace Resource
PATCH	Partial Update
DELETE	Remove Resource
HEAD	Retrieve Headers
OPTIONS	Supported Operations

Production Example

GET /employees

POST /employees

PUT /employees/101

DELETE /employees/101

Interview Follow-up

Why are HTTP methods important in REST?

2. What is the GET Method?

Short Answer

GET retrieves one or more resources from the server without modifying data.

Internal Working

Client

↓

GET /employees/101

↓

Server

↓

Database

↓

JSON Response

Spring Boot Example

@GetMapping("/{id}")
public Employee getEmployee(@PathVariable Long id){
    return service.find(id);
}

Production Example

GET /products

GET /orders/101

GET /customers

Characteristics

Safe
Idempotent
Cacheable

Common Mistakes

❌ Using GET to update records.

3. What is the POST Method?

Short Answer

POST creates a new resource on the server.

Internal Working

Client

↓

POST /employees

↓

Server

↓

Insert Database

↓

201 Created

Spring Boot Example

@PostMapping
public Employee create(@RequestBody Employee employee){
    return service.save(employee);
}

Production Example

POST /orders

POST /payments

POST /customers

Characteristics

Not Safe
Not Idempotent

Common Mistakes

Using POST for updates.

4. What is the PUT Method?

Short Answer

PUT replaces an existing resource completely.

Internal Working

Existing Employee

↓

PUT Request

↓

Entire Object Replaced

↓

Updated Record

Spring Boot Example

@PutMapping("/{id}")
public Employee update(
        @PathVariable Long id,
        @RequestBody Employee employee){

    return service.update(id, employee);
}

Characteristics

Idempotent
Not Safe

Production Example

Updating an employee profile.

Common Mistakes

Sending only one field in a PUT request.

5. What is the PATCH Method?

Short Answer

PATCH updates only selected fields of a resource.

Example

Before

Employee

Name

Salary

Department

PATCH

Salary Only

After

Only Salary Updated

Spring Boot Example

@PatchMapping("/{id}")
public Employee updateSalary(
        @PathVariable Long id,
        @RequestBody SalaryRequest request){

    return service.updateSalary(id, request);
}

Production Example

PATCH /employees/100

{
 "salary":95000
}

Common Mistakes

Using PATCH to replace the entire object.

6. What is the DELETE Method?

Short Answer

DELETE removes a resource from the server.

Internal Working

DELETE /employees/101

↓

Server

↓

Delete Record

↓

204 No Content

Spring Boot Example

@DeleteMapping("/{id}")
public void delete(@PathVariable Long id){
    service.delete(id);
}

Characteristics

Idempotent
Not Safe

Production Example

Deleting inactive users.

Common Mistakes

Returning 200 with unnecessary response body.

7. What is the HEAD Method?

Short Answer

HEAD returns only response headers without the response body.

Production Uses

Check file size
Validate caching
Verify resource existence

Example

HEAD /documents/report.pdf

Returns

Content-Length

Content-Type

Last-Modified

Interview Follow-up

Why use HEAD instead of GET?

8. What is the OPTIONS Method?

Short Answer

OPTIONS returns the HTTP methods supported by a resource.

Example

OPTIONS /employees

Response

Allow:
GET
POST
PUT
DELETE

Production Uses

CORS
Browser preflight requests
API discovery

9. What are Safe HTTP Methods?

Short Answer

Safe methods do not modify server data.

Safe Methods

GET
HEAD
OPTIONS

Production Example

Searching products.

Viewing employee details.

Downloading reports.

10. What are Idempotent Methods?

Short Answer

Repeated execution produces the same final result.

Idempotent Methods

GET
PUT
DELETE
HEAD
OPTIONS

Example

DELETE /employees/100

Calling it multiple times results in the resource remaining deleted.

Non-Idempotent

POST

11. What is the Difference Between PUT and PATCH?

Feature	PUT	PATCH
Update Type	Complete	Partial
Replace Object	Yes	No
Payload	Entire Object	Changed Fields
Idempotent	Yes	Usually

Production Example

PUT

Replace Customer Profile

PATCH

Update Mobile Number Only

12. What is the Difference Between POST and PUT?

Feature	POST	PUT
Purpose	Create	Replace
Idempotent	No	Yes
URI	Collection	Resource
Multiple Calls	Multiple Resources	Same Resource

Example

POST

POST /employees

PUT

PUT /employees/101

13. What are Common HTTP Method Mistakes?

Using POST for updates.
Using GET to delete records.
Using PUT for partial updates.
Ignoring idempotency.
Using DELETE with request bodies unnecessarily.
Returning incorrect HTTP status codes.
Using verbs in URIs.

14. How are HTTP Methods Used in Enterprise Applications?

Example Online Banking API

GET     /accounts

POST    /transfers

PUT     /customers/101

PATCH   /cards/101

DELETE  /beneficiaries/22

Architecture

Client

↓

API Gateway

↓

Spring Boot API

↓

Business Service

↓

Database

Each HTTP method maps to a specific business operation.

15. Design HTTP Methods for an Employee Management API

REST Endpoints

GET    /employees

GET    /employees/{id}

POST   /employees

PUT    /employees/{id}

PATCH  /employees/{id}

DELETE /employees/{id}

HEAD   /employees

OPTIONS /employees

Best Practices

Use GET only for retrieval.
Use POST only for creation.
Use PUT for complete replacement.
Use PATCH for partial updates.
Use DELETE to remove resources.
Return meaningful HTTP status codes.
Design idempotent APIs whenever possible.
Avoid using verbs in URIs.

HTTP Methods Summary

Method	Purpose	Safe	Idempotent
GET	Retrieve	✅	✅
POST	Create	❌	❌
PUT	Replace	❌	✅
PATCH	Partial Update	❌	Usually
DELETE	Remove	❌	✅
HEAD	Headers Only	✅	✅
OPTIONS	Supported Methods	✅	✅

Interview Tips

When asked about HTTP Methods:

Explain the purpose of each method.
Differentiate GET vs POST.
Explain PUT vs PATCH with examples.
Discuss Safe vs Idempotent methods.
Mention appropriate HTTP status codes.
Use production examples from Spring Boot or Microservices.
Explain why choosing the correct method improves API consistency.
Relate HTTP methods to REST best practices.

Key Takeaways

HTTP Methods define the operation performed on a REST resource.
GET retrieves data and should never modify server state.
POST creates new resources and is not idempotent.
PUT replaces an entire resource and is idempotent.
PATCH performs partial updates, reducing payload size.
DELETE removes resources and is idempotent.
HEAD retrieves only response headers.
OPTIONS is primarily used for CORS and API capability discovery.
Understanding Safe and Idempotent methods is essential for REST API interviews.
Correct use of HTTP methods leads to predictable, maintainable, and production-ready APIs.