RESTful API Interview Questions

Delve into our curated collection of RESTful API Interview Questions, meticulously crafted to prepare you for your upcoming interview. Explore fundamental concepts such as HTTP methods, status codes, authentication, versioning, and best practices.

Whether you’re a seasoned API developer or just starting your journey, this comprehensive guide will equip you with the knowledge and confidence to tackle any interview question.

Prepare to showcase your expertise and secure your dream job in the world of web services with our RESTful API Interview Questions guide.

RESTful API Interview Questions For Freshers

1. What is a RESTful API?

A RESTful API is an architectural style for designing networked applications. It stands for Representational State Transfer. It relies on stateless communication between the client and server, using standard HTTP methods for data manipulation.

// Import necessary modules
const express = require('express');

// Create an Express application
const app = express();

// Define a simple endpoint
app.get('/api/message', (req, res) => {
    res.send('Hello, this is a simple RESTful API!');
});

// Start the server
const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Server running on port ${port}...`));

2. Explain the key principles of RESTful architecture?

The key principles of RESTful architecture include statelessness, client-server architecture, cacheability, layered system, uniform interface, and code on demand (optional).

3. What are the main HTTP methods used in RESTful APIs?

The main HTTP methods are GET, POST, PUT, DELETE, PATCH, and sometimes OPTIONS and HEAD.

4. What is the purpose of the HTTP GET method in RESTful APIs?

The GET method is used to retrieve data from a server. It should only retrieve data and have no other effect on the server.

5. Explain the difference between PUT and POST methods?

PUT is used to update or replace a resource, while POST is used to create a new resource or perform custom actions.

const express = require('express');
const bodyParser = require('body-parser');

const app = express();
app.use(bodyParser.json());

let items = []; // Sample data store

// POST method to add a new item
app.post('/api/items', (req, res) => {
    const newItem = req.body; // Assuming request body contains the new item details
    items.push(newItem);
    res.status(201).json(newItem); // Respond with the newly created item
});

// PUT method to update an existing item
app.put('/api/items/:id', (req, res) => {
    const itemId = parseInt(req.params.id);
    const updatedItem = req.body; // Assuming request body contains the updated item details
    
    // Find the index of the item to be updated
    const index = items.findIndex(item => item.id === itemId);
    if (index === -1) {
        res.status(404).send('Item not found');
    } else {
        items[index] = updatedItem; // Replace the existing item with the updated one
        res.json(updatedItem); // Respond with the updated item
    }
});

const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Server running on port ${port}`));

6. What is the purpose of the HTTP DELETE method?

DELETE is used to remove a resource from the server.

7. What is a URI in the context of RESTful APIs?

URI (Uniform Resource Identifier) is a unique identifier for a resource that is accessed via a web service. It is used to locate and identify resources.

8. What is the difference between URI and URL?

A URI (Uniform Resource Identifier) is a string of characters that identifies a particular resource, while a URL (Uniform Resource Locator) is a specific type of URI that includes the network location of the resource.

9. Explain the term “stateless” in the context of RESTful APIs?

Stateless means that each request from a client to a server must contain all the information necessary to understand the request. The server should not store any client state between requests.

10. What is JSON?

JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write and easy for machines to parse and generate.

// JSON data
const jsonData = `{
    "name": "John",
    "age": 30,
    "city": "New York"
}`;

// Parsing JSON data
const parsedData = JSON.parse(jsonData);

// Accessing JSON properties
console.log("Name:", parsedData.name); // Output: Name: John
console.log("Age:", parsedData.age); // Output: Age: 30
console.log("City:", parsedData.city); // Output: City: New York

11. What is the purpose of the HTTP status codes in RESTful APIs?

HTTP status codes indicate the outcome of the HTTP request made by the client. They provide information about the success or failure of the request.

12. Explain the term “content negotiation” in RESTful APIs?

Content negotiation is the process of selecting the best representation for a resource based on the client’s preferences, such as language, media type, or encoding.

13. What are the advantages of using RESTful APIs?

Some advantages include scalability, simplicity, compatibility with various platforms and languages, and separation of concerns between client and server.

14. What is HATEOAS?

HATEOAS (Hypermedia as the Engine of Application State) is a constraint of the REST architecture that requires a client to interact with a network application entirely through hypermedia provided dynamically by application servers.

{
  "id": 123,
  "name": "Product 1",
  "price": 50.00,
  "links": [
    { "rel": "self", "href": "/api/products/123" },
    { "rel": "edit", "href": "/api/products/123/edit" },
    { "rel": "delete", "href": "/api/products/123/delete" }
  ]
}

15. Explain the concept of versioning in RESTful APIs?

Versioning in RESTful APIs is the practice of providing multiple versions of the same API to support backward compatibility while introducing new features or changes.

16. What is CORS?

CORS (Cross-Origin Resource Sharing) is a mechanism that allows restricted resources on a web page to be requested from another domain outside the domain from which the first resource was served.

const express = require('express');
const app = express();

// Middleware to enable CORS
app.use((req, res, next) => {
    res.header('Access-Control-Allow-Origin', '*'); // Allow requests from any origin
    res.header('Access-Control-Allow-Headers', 'Origin, X-Requested-With, Content-Type, Accept'); // Allow specified headers
    res.header('Access-Control-Allow-Methods', 'GET, POST, PUT, DELETE'); // Allow specified HTTP methods
    next();
});

// Define your routes here...

// Start the server
const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Server running on port ${port}`));

17. How do you secure a RESTful API?

You can secure a RESTful API by using authentication mechanisms like API keys, OAuth, JWT (JSON Web Tokens), HTTPS, rate limiting, input validation, and proper error handling.

18. What tools or libraries can be used to build RESTful APIs?

Popular tools and libraries include Express.js (for Node.js), Django Rest Framework (for Python), Spring Boot (for Java), Flask (for Python), ASP.NET Core (for C#), and Laravel (for PHP).

19. Explain the term “pagination” in RESTful APIs?

Pagination is the process of dividing a large set of results into smaller, manageable subsets called pages. It helps improve performance and usability by reducing the amount of data transferred between the client and server.

const express = require('express');
const app = express();

// Sample data (array of items)
const items = [...]; // Array of items (e.g., database records)

// Route for fetching paginated items
app.get('/api/items', (req, res) => {
    const page = parseInt(req.query.page) || 1; // Current page number, default is 1
    const pageSize = parseInt(req.query.pageSize) || 10; // Number of items per page, default is 10
    
    // Calculate start and end indices for the current page
    const startIndex = (page - 1) * pageSize;
    const endIndex = startIndex + pageSize;

    // Extract items for the current page
    const pageItems = items.slice(startIndex, endIndex);

    // Construct and send paginated response
    res.json({
        page: page,
        pageSize: pageSize,
        totalItems: items.length,
        totalPages: Math.ceil(items.length / pageSize),
        data: pageItems
    });
});

// Start the server
const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Server running on port ${port}`));

20. What are the best practices for designing RESTful APIs?

Best practices include using meaningful URIs, following HTTP method semantics, providing clear documentation, using proper error handling, implementing caching where appropriate, and designing for scalability and security.

RESTful API Interview Questions For 3 Years Experience

1. What is the purpose of a RESTful API?

A RESTful API serves as an interface for clients to interact with server-side resources over the internet using standard HTTP methods.

2. How do you handle authentication in RESTful APIs?

Authentication in RESTful APIs can be handled using mechanisms like API keys, OAuth, JWT (JSON Web Tokens), or session-based authentication.

3. Explain the term “idempotent” in the context of RESTful APIs?

An idempotent operation is one that produces the same result regardless of how many times it is executed. In RESTful APIs, GET, PUT, and DELETE methods are typically idempotent.

const express = require('express');
const app = express();

// Sample data (array of items)
let items = [
    { id: 1, name: 'Item 1' },
    { id: 2, name: 'Item 2' }
];

// GET method is idempotent
app.get('/api/items', (req, res) => {
    res.json(items);
});

// PUT method is idempotent (updates an existing resource)
app.put('/api/items/:id', (req, res) => {
    const itemId = parseInt(req.params.id);
    const updatedItem = req.body;
    const index = items.findIndex(item => item.id === itemId);
    if (index !== -1) {
        items[index] = updatedItem;
        res.json(updatedItem);
    } else {
        res.status(404).send('Item not found');
    }
});

// DELETE method is idempotent (deletes an existing resource)
app.delete('/api/items/:id', (req, res) => {
    const itemId = parseInt(req.params.id);
    const index = items.findIndex(item => item.id === itemId);
    if (index !== -1) {
        items.splice(index, 1);
        res.json({ message: 'Item deleted' });
    } else {
        res.status(404).send('Item not found');
    }
});

// Start the server
const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Server running on port ${port}`));

4. What are the advantages of using RESTful APIs over other architectures?

RESTful APIs offer advantages such as scalability, simplicity, interoperability, and separation of concerns between client and server.

5. How do you handle errors and exceptions in RESTful APIs?

Errors and exceptions in RESTful APIs can be handled by returning appropriate HTTP status codes along with error messages in the response body.

6. What is the purpose of the OPTIONS method in RESTful APIs?

The OPTIONS method is used to retrieve information about the communication options available for a resource or server.

7. What are HATEOAS and its benefits?

HATEOAS (Hypermedia as the Engine of Application State) is a constraint in RESTful APIs that provides hypermedia links within responses, enabling clients to navigate the API dynamically. It enhances discoverability and decouples clients from server implementation details.

8. Explain the concept of rate limiting in RESTful APIs?

Rate limiting is a technique used to restrict the number of requests a client can make to an API within a specified time period. It helps prevent abuse and ensures fair usage of resources.

9. How do you implement pagination in RESTful APIs?

Pagination in RESTful APIs involves limiting the number of results returned per page and providing parameters like page number and page size in the API request to navigate through large datasets.

10. What security measures can you implement to protect RESTful APIs?

Security measures include using HTTPS, implementing authentication and authorization mechanisms, input validation, rate limiting, and protecting against common vulnerabilities like XSS (Cross-Site Scripting) and CSRF (Cross-Site Request Forgery).

11. Explain the concept of content-type negotiation?

Content-type negotiation is the process of selecting the most appropriate representation of a resource based on the client’s preferred content type, such as JSON or XML.

const express = require('express');
const app = express();

// Sample data
const products = [
    { id: 1, name: 'Product 1', price: 10 },
    { id: 2, name: 'Product 2', price: 20 }
];

// Endpoint to fetch products
app.get('/api/products', (req, res) => {
    const acceptHeader = req.get('Accept');

    // Check client's preferred content type
    if (acceptHeader.includes('application/json')) {
        res.json(products);
    } else if (acceptHeader.includes('text/html')) {
        // Render HTML representation
        const productListHTML = products.map(product => `<li>${product.name} - $${product.price}</li>`).join('');
        res.send(`<ul>${productListHTML}</ul>`);
    } else {
        res.status(406).send('Not Acceptable');
    }
});

// Start the server
const port = process.env.PORT || 3000;
app.listen(port, () => console.log(`Server running on port ${port}`));

12. What role does caching play in RESTful APIs, and how do you implement it?

Caching improves performance by storing responses to requests and reusing them for subsequent identical requests. It can be implemented using HTTP caching headers like Cache-Control and ETag.

13.How do you ensure backward compatibility when making changes to RESTful APIs?

Backward compatibility can be ensured by versioning APIs, maintaining clear documentation, providing deprecation notices for deprecated features, and offering migration paths for clients.

14. Explain the term “statelessness” in the context of RESTful APIs?

Statelessness means that each request from a client to a server contains all the information necessary to understand the request, and the server does not maintain any client state between requests.

15. What is the purpose of the HEAD method in RESTful APIs?

The HEAD method is similar to GET but returns only the response headers without the response body. It is often used to check the status of a resource or retrieve metadata.

RESTful API Developers Roles and Responsibilities

The role of a RESTful API developer involves designing, implementing, and maintaining APIs that adhere to the principles of REST (Representational State Transfer). Here are the key roles and responsibilities of a RESTful API developer:

API Design: Designing APIs that are intuitive, easy to use, and follow best practices. This includes defining resource endpoints, request and response formats, authentication mechanisms, and error handling strategies.

Implementation: Writing clean, maintainable, and efficient code to implement the defined API endpoints. This involves choosing appropriate programming languages, frameworks, and libraries to build the APIs.

Data Modeling: Designing data models and schemas to represent resources and their relationships in the API. This includes defining database tables, document structures, or other data storage mechanisms.

Authentication and Authorization: Implementing authentication mechanisms such as OAuth, JWT, or API keys to secure API endpoints. Ensuring proper authorization checks are in place to restrict access to certain resources based on user roles and permissions.

Documentation: Creating comprehensive documentation for the API, including endpoint descriptions, request and response formats, error codes, and usage examples. Documentation should be clear, concise, and easily accessible to API consumers.

Testing: Writing and executing test cases to ensure the reliability, performance, and security of the API. This includes unit testing individual endpoints, integration testing with other systems, and stress testing under load.

Monitoring and Logging: Implementing logging mechanisms to track API usage, errors, and performance metrics. Setting up monitoring tools to detect and troubleshoot issues in real-time, such as response times, error rates, and resource usage.

Versioning: Managing API versions to maintain backward compatibility while introducing new features or changes. This includes defining versioning strategies and handling deprecated endpoints or fields gracefully.

Performance Optimization: Identifying and optimizing performance bottlenecks in the API, such as database queries, network latency, or response times. Implementing caching mechanisms and other optimizations to improve scalability and responsiveness.

Collaboration: Working closely with frontend developers, product managers, and other stakeholders to understand requirements, gather feedback, and iterate on API designs and implementations.

Security: Ensuring the security of the API by implementing best practices for data encryption, input validation, and protection against common security vulnerabilities such as injection attacks, XSS, CSRF, and others.

Compliance: Ensuring compliance with industry standards and regulations such as GDPR, HIPAA, PCI-DSS, or others depending on the nature of the application and the data being handled.

Maintenance and Support: Providing ongoing maintenance and support for the API, including bug fixes, performance optimizations, and feature enhancements based on user feedback and changing business requirements.

Overall, a RESTful API developer plays a crucial role in building robust, scalable, and secure APIs that enable seamless communication between different components of a software system.

Frequently Asked Questions