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Restful API 101 — Everything You Need to Know

· 23 min read
Ishika Kesarwani

REST stands for RESTful API (Representational State Transfer Application Programming Interface) which is a web-based architecture that enables communication between different systems and applications. It is a way of building web services that allow clients to interact with servers in a stateless and scalable manner. In the other hand API, stands for Application Programming Interface, which allows the client to talk to the server.

What is RESTful API

RESTful API is like a system of communication between different computer programs, kind of like how you and your friends text each other.

Each program sends and receives messages, known as "requests" and "responses," to ask for information or give instructions. These messages are sent through the internet, like texting over a network.

Just like how you text your friend to ask what they're up to or to tell them to meet you at the park, the computer programs use the RESTful API to communicate and exchange information with each other. This helps the programs work together and get things done without having to be in the same place!

RESTful APIs are based on the principles of REST, which is an architectural style for designing web services. A REST determines how a API may look like that defines a set of constraints and guidelines that allow applications to communicate over the web using HTTP methods. RESTful APIs are lightweight, flexible, and scalable, making them a popular choice for building modern web applications.

The Constraints of RESTful API

RESTful APIs have several constraints that ensure consistency and compatibility between systems. These constraints include:

  • Client-Server Architecture: The client and server are separated and communicate through APIs. A client should only be aware of resource URIs.
  • Statelessness: Each request from the client contains all the information needed to complete the request, and the server does not store any state information between requests.
  • Cacheable: Clients can cache responses from the server to improve performance and reduce the load on the server, thus improving the scalability and performance.
  • Layered System: The client does not need to know the details of the underlying systems and can access the server through intermediaries.
We suppose to make API faster meme

The Benefits of RESTful API

  • Scalability: RESTful APIs can easily scale to meet the demands of growing applications as stateless communication and a replicated repository provides high scalability.
  • Interoperability: RESTful APIs can be used by a variety of systems, platforms, and programming languages, making them highly interoperable.
  • Independence: The REST protocol provides autonomous development across several areas of project because of the separation in between client and server.
  • Easy Maintenance: RESTful APIs are easy to maintain and update, as they are decoupled from the underlying systems and clients.

RESTful API Methods

RESTful APIs use standard HTTP methods to perform operations on resources. The four main methods are:

Mostly used RESTful API methods
Mostly used RESTful API methods

GET Method: Retrieving Data

The GET method is used to read that is to retrieve data from the server. It is a safe and idempotent method, meaning that multiple GET requests to the same resource will always return the same result without any risk of data modification or corruption.

POST Method: Creating Data

The POST method is used to create new resources on the server, particularly it is used to create subordinate resources. It is not a safe or idempotent method, as it can have side effects on the server and can create multiple resources with the same request, which can lead to two resources having the same information.

PUT Method: Updating Data

The PUT method is used to update existing resources on the server. It is not a safe method, but it is idempotent, meaning that multiple PUT requests to the same resource with the same data will have the same effect.

DELETE Method: Deleting Data

The DELETE method is used to delete resources from the server. It is not a safe or idempotent method, as it can have side effects and can delete multiple resources with the same request.


It is worth noting that the HTTP methods are not limited to the four main methods mentioned above. There are other methods that can be used to perform operations on resources, such as PATCH, HEAD, OPTIONS, and TRACE. However, these methods are not commonly used in RESTful APIs.

Using JSON in RESTful API: Data Formats and Examples

JSON (JavaScript Object Notation) is a lightweight data interchange format that is easy for humans to read and write and for machines to parse and generate. It is widely used in RESTful APIs as the default data format for exchanging information between client and server.

JSON Data Format

JSON is a text-based data format following JavaScript object syntax. JSON data consists of key-value pairs, where each key is a string and each value can be a string, number, object, array, or one of the values true, false, or null.

Objects are represented as curly braces {} containing a comma-separated list of key-value pairs, while arrays are represented as square brackets [], containing a comma-separated list of values.

Here's an example of a JSON object:

Example JSON Object in RESTful API
{  "name": "John Doe",  "age": 30,  "address": {    "street": "123 Main St",    "city": "New York",    "state": "NY"  },  "phoneNumbers": [    {      "type": "home",      "number": "212 555-1234"    },    {      "type": "office",      "number": "646 555-4567"    }  ]}

In this example, the JSON object represents a person with a name, age, address, and phone numbers. The address is an object with three key-value pairs, while the phone numbers is an array of objects. The phone numbers array contains two objects, each with type, and number keys and values.


Imagine you have a library where you keep all your favorite books. The books are organized into categories, such as fiction, non-fiction, etc. You can easily add new books to the library, update the information about existing books, and retrieve information about books in the library.

Generate a book collection in JSON format:

Example JSON Object in RESTful API
{  "books": [    {      "id": 1,      "title": "The Lord of the Rings",      "author": "J.R.R. Tolkien",      "category": "fiction"    },    {      "id": 2,      "title": "The Hobbit",      "author": "J.R.R. Tolkien",      "category": "fiction"    },    {      "id": 3,      "title": "The Hitchhiker's Guide to the Galaxy",      "author": "Douglas Adams",      "category": "fiction"    },    {      "id": 4,      "title": "The Art of Computer Programming",      "author": "Donald Knuth",      "category": "non-fiction"    }  ]}

In this example, the JSON object represents a collection of books. The books are organized into categories, such as fiction and non-fiction. The books are stored in an array, where each book is an object with four key-value pairs.

RESTful APIs use endpoints to perform operations on resources. For example, the following endpoints can be used to manage a collection of books:

MethodEndpoint URIOperationsEndpoint Path
GET/booksRetrieve the collection of books
POST/booksCreate a new book in the collection
GET/books/:idRetrieve a specific book from the collection
PUT/books/:idUpdate a specific book in the collection
DELETE/books/:idDelete a specific book from the collection

In this example, the endpoints are used to perform operations on the collection of books. The first endpoint is used to retrieve the collection of books, while the second endpoint is used to create a new book in the collection.

Similarly, RESTful APIs use JSON data to manage a collection of resources, where each resource represents a specific item.

In RESTful APIs, JSON is typically used to send and receive data between client and server.

JSON Examples in RESTful API

Here's an example of a JSON payload in a RESTful API request:

GET Request for a Collection of Star Wars Films
GET /films200 OK  // Response Status Code[  {    "id": 1,    "title": "A New Hope",    "year": 1977  },  {    "id": 2,    "title": "The Empire Strikes Back",    "year": 1980  },  {    "id": 3,    "title": "Return of the Jedi",    "year": 1983  },  {    "id": 4,    "title": "The Phantom Menace",    "year": 1999  },  {    "id": 5,    "title": "Attack of the Clones",    "year": 2002  },  {    "id": 6,    "title": "Revenge of the Sith",    "year": 2005  },  {    "id": 7,    "title": "The Force Awakens",    "year": 2015  },  {    "id": 8,    "title": "The Last Jedi",    "year": 2017  },  {    "id": 9,    "title": "The Rise of Skywalker",    "year": 2019  }]

In this example, a GET request to the /films endpoint returns an array of JSON objects, each representing a Star Wars film resource. Each object contains the film's ID, title, and year of release.

Designing a RESTful API: Best Practices and Tips

Designing a RESTful API involves several key principles and considerations. Here are some tips for designing a RESTful API that is both functional and easy to use ensuring that the API is efficient, and scalable.

API Design Principles

  • REST APIs are built around resources, which can be any type of object, data, or service that the client can access.
  • A resource has an identifier, which is a URI that uniquely identifies that resource.

For example, the URI for a particular customer order might be:
  • REST APIs use a stateless request model. When a program sends a request for information, it should not expect the server to remember any information from previous requests. This is important because it allows the service to work for many different clients at the same time, without getting confused or mixed up. It also helps the service to keep working quickly and smoothly, even if a lot of people are using it at once.

Think of it like a store with many cashiers. Each customer comes up to the cashier, makes their purchase, and leaves. The cashier doesn't keep track of what the customer bought before, they only focus on the current transaction. This way, many customers can be served quickly and efficiently, without any confusion.

URI Design

  • Use nouns, not verbs: RESTful APIs should use nouns in the URI to describe resources, not verbs and should refer out to the resources.


    Consider using /movies in place of /get-movies

  • Use plural nouns: RESTful APIs should use plural nouns in the URI to describe collections of resources.


    For example, /movies is used to represent a collection of movies, while /movie is used to represent a single movie.

  • Use hierarchical structures: RESTful APIs should use hierarchical structures in the URI to describe relationships between resources with multiple levels.


    For example, /movies/1/actors is used to represent a collection of actors in a movie with ID 1, while /movies/1/actor/2 is used to represent a single actor with ID 2 in a movie with ID 1.

  • Avoid Redundancy: URIs should avoid redundancy, and resources should be represented once and only once.


    For example, /movies/1/actors/2 is used to represent a single actor with ID 2 in a movie with ID 1, while /actors/2 is used to represent a single actor with ID 2.

  • Use Filters and Pagination: URIs should use filters and pagination to control the amount of data returned, when necessary.


    For example, /movies?year=2019 is used to represent a collection of movies released in 2019, while /movies?year=2019&page=2 is used to represent the second page of movies released in 2019.

    For example, /movies?year=2019&limit=10 is used to represent the first 10 movies released in 2019, while /movies?year=2019&limit=10&page=2 is used to represent the second 10 movies released in 2019.

Error Handling

  • Return Consistent Response Codes: Return the same HTTP response code for a similar error and document it in the API documentation.
  • Use Appropriate HTTP Response Codes: Use appropriate HTTP response codes to indicate the success or failure of a request
200OKThe request was successful.
201CreatedThe request was successful and a new resource was created.
204No ContentThe request was successful but there is no representation to return.
400Bad RequestThe request was invalid or cannot be served.
401UnauthorizedAuthentication is required or has failed.
403ForbiddenThe request is understood, but it has been refused or access is not allowed.
404Not FoundThe URI requested is invalid or the resource requested does not exist.
429Too Many RequestsThe request cannot be served due to the rate limit having been exhausted.
500Internal Server ErrorSomething went wrong on the server.
  • Provide Error Details: Provide detailed error information in a structured format, such as JSON or XML, to help the client understand the error.
  • Avoid Exposing Sensitive Information: Avoid exposing sensitive information in error responses, such as stack traces, passwords, and keep error messages generic.
  • Retry Logic: Allow the client to handle retry logic in case of network errors, timeouts, or other temporary errors.
  • Logging: Log errors to assist in debugging and problem resolution. RESTful APIs should log errors to help diagnose and resolve issues.
  • Use standard HTTP status codes: RESTful APIs should use standard HTTP status codes to indicate success or failure of a request.


  • Use versioning: Versioning should be used in RESTful APIs to allow updates to the API without harming current clients.

  • Use a version in the URI: To indicate which version of the API is being used, RESTful APIs should include the version number in the URI.


    For example, /v1/films is used to represent the first version of the films resource.

  • Use a version in the request header: To indicate which version of the API is being used, RESTful APIs should include the version number in the request header.


    For example, Accept: application/ is used to represent the first version of the API.

  • Preserve backwards compatibility: To reduce the impact of changes on current clients, RESTful APIs should maintain as much backwards compatibility as feasible.

Securing a RESTful API: Authentication and Authorization

Securing a RESTful API entails protecting sensitive data and ensuring that only authorised users can access the API.

API Security Threats

  • Injection Attacks: Injection attacks occur when an attacker is able to insert malicious code into a RESTful API request.
  • Cross-Site Scripting (XSS) Attacks: XSS attacks occur when an attacker is able to inject malicious scripts into a RESTful API response which is executed in the user’s browser.
  • Man-in-the-Middle (MitM) Attacks: MitM attacks occur when an attacker intercepts communication between a client and a server.
  • Denial of Service (DoS) Attacks: DoS attacks occur when an attacker floods a server with traffic, preventing it from responding to genuine requests.
  • Cross-Site Request Forgery (CSRF): CSRF attacks occur when an attacker tricks a user into making a request to the API from a malicious site.

Authentication Methods

  • Basic Authentication: Basic authentication involves sending a username and password with each API request.

  • Token-Based Authentication: Token-based authentication involves generating a unique token for each user and sending the token with each API request.

  • OAuth: OAuth is a standard for authorization that allows a user to grant access to their resources to a third-party client without sharing their credentials.

  • JWT (JSON Web Tokens): JWT is a compact, self-contained token format that is used for authentication and authorization.

Authorization Methods

  • Role-Based Access Control (RBAC): RBAC involves assigning users to roles and granting permissions to those roles.
  • Attribute-Based Access Control (ABAC): ABAC involves evaluating user attributes, such as their location or device, to determine their access to a resource.
  • Policy-Based Access Control: Policy-based access control involves defining policies that determine access to resources based on a set of conditions.

Security Best Practices

  • Use HTTPS: Encrypt communication between the client and the server by using HTTPS (HTTP Secure).
  • Validate Inputs: Validate all inputs to avoid using malicious data in an API request.
  • Tokens: Tokens may be used to authenticate users and safeguard their data. Tokens should be short lived, unique, and cryptographically signed.
  • Enable Access Control: Implement access control to restrict who can access sensitive resources.
  • Use Encryption: Encrypt sensitive data while it is in transit and at rest.
  • Log and Monitor: Record all API calls and keep an eye out for suspicious activities. This will assist you in promptly detecting and responding to security problems.
  • Maintain Software Updates: Keep all software, including the operating system, middleware, and APIs, up to date with the most recent security patches.

RESTful API and Microservices: How They Work Together

Microservices and RESTful API

RESTful APIs is a type of web service that enables client applications to interact with server-side resources. Microservices, on the other hand, is a method of developing and deploying applications as a collection of tiny, independent services that function together. Each microservice serves a distinct, well-defined purpose and communicates with other microservices using APIs such as a RESTful API.

When RESTful API and microservices are used together, each microservice may be built to offer a RESTful API that allows client applications to communicate with the microservice. This results in a loosely coupled system in which each microservice can grow independently of the others.

Microservices Benefits

  • Scalability: Microservices can be scaled independently, allowing for more efficient resource allocation.
  • Resilience: If one service fails, the others can continue to function, increasing overall system stability.
  • Flexibility: Changes to one service can be made without affecting the others, allowing for faster and more efficient development. Improved Maintainability: Smaller services are easier to maintain and deploy than a monolithic codebase.
  • Ease of deployment: Microservices can be deployed, updated and tested individually, which increases deployment speed and reduces downtime.
  • Ease of Testing: Smaller, isolated services are easier to test, increasing the overall quality of the system.
  • Improved Modularity: The separation of services makes it easier to understand the system as a whole and to make modifications.

Debugging and Troubleshooting RESTful API

Debugging and troubleshooting RESTful API can be a complex task, but there are tools and techniques available to help.

Common Issues in RESTful API

  • Incorrect API Endpoints: Incorrect API endpoints can lead to 404 errors or unexpected results.
  • Missing or Incorrect Headers: Missing or incorrect headers can lead to errors or unexpected results.
  • Incorrect HTTP Method: Incorrect HTTP method (e.g. using GET instead of POST) can lead to errors or unexpected results.
  • Incorrect Data Format: Incorrect data format can lead to errors or unexpected results.

Debugging Tools

  • Postman: Postman is a tool for testing RESTful APIs, allowing you to send requests and view the responses.
  • Fiddler: Fiddler is a tool for debugging web traffic, allowing you to view the requests and responses between client and server.
  • Charles: Charles is a tool for debugging web traffic, allowing you to view the requests and responses between client and server.

Troubleshooting Techniques

  • Use logging to keep track of requests, responses, failures, and any unexpected outcomes.
  • Use Debugging Tools: To view the requests and responses between the client and server, use debugging tools like Postman, Fiddler, or Charles.
  • Test Individual Components: To identify the issue's origin, test individual components, such as the API endpoint or data format.
  • Reproduce the Issue: In order to isolate the issue and facilitate debugging, reproduce the issue.

RESTful API and Caching: Optimizing Performance

Caching is a technique that can help optimize the performance of RESTful APIs by reducing the number of requests to the server.

Caching in RESTful API

Caching in RESTful API refers to the technique of storing frequently used data on the client side, instead of requesting the same data from the server every time it is needed. This improves the performance of the API by reducing the number of requests to the server and allowing for faster retrieval of the data.

For example, when a client makes a request to the API for a resource, the API may include cache control headers in the response that instruct the client to store the response data in its cache. The next time the client needs the same resource, it can retrieve the data from its cache rather than sending a new request to the server, reducing the load on the server and improving the response time for the client.

By reducing the number of requests to the server and improving the response time, caching can help improve the overall performance and scalability of a RESTful API.

Caching Strategies

Caching Strategies
  • Client-side caching: Client-side caching involves storing frequently used data on the client device, such as a web browser or mobile device, for faster retrieval. The client device can cache data from the API in its local storage and use it in subsequent requests, reducing the number of requests to the server and improving response time.
  • Server-side caching: Server-side caching, on the other hand, involves storing frequently used data on the server. This can be done in a cache server, database or any other storage mechanism that is optimized for fast access. The server can cache the data it retrieves from the API, and return it to clients in response to subsequent requests, reducing the load on the API and improving performance.
  • Hybrid caching: Hybrid caching is a combination of client-side and server-side caching. In this approach, the client device caches data locally and the server also caches data in its own storage. This combination provides both fast access to frequently used data and reduces the load on the server, resulting in improved performance and scalability.

Caching Best Practices

  • Use caching headers: Caching headers are HTTP headers that provide information about the caching behavior of a resource. They can be used to control the caching behavior of data returned from a RESTful API. For example, the ETag header provides a unique identifier for a resource, and the Last-Modified header provides information about when a resource was last modified. These headers can be used to control when a client device should cache data, and when it should request a fresh copy from the server.
  • Invalidate cache regularly: To ensure that clients are served with fresh data, it is important to regularly invalidate the cache. This can be done by making changes to the resource that changes the unique identifier in the ETag header, or by providing a new Last-Modified header. Invalidating the cache ensures that clients are not served stale data and that they receive the most up-to-date information from the API.
  • Consider expiration time: The expiration time of cached data is an important factor to consider when implementing caching in a RESTful API. It should be set to a reasonable time that balances the need for fresh data with the performance benefits of caching. If the expiration time is set too short, clients may make too many requests to the server, reducing performance. If it is set too long, clients may be served with stale data. Finding the right balance between these two factors is important to ensure that the API provides fast, reliable, and up-to-date information to clients.

RESTful API and Documenting: How to create good API documentation

API documentation is crucial for developers to understand how to interact with a RESTful API and for consumers to understand what the API can do.

Importance of API documentation

API documentation is essential for a number of reasons:

  • Facilitates understanding: API documentation aids developers in understanding the functionality and capabilities of an API.
  • Enhances developer experience: By providing clear and simple information about the API, good API documentation may enhance the developer experience.
  • Increases adoption: Well-documented APIs are more likely to be accepted and utilised in apps by developers.

Types of API documentation

There are several types of API documentation, including:

  • Reference Documentation: Extensive information about endpoints, request/response formats, error codes, and so on.
  • Tutorials: Step-by-step instructions for doing certain activities with the API.
  • Code Samples: Examples in various programming languages that demonstrate how to use the API.
  • User Guides: Provides an overview of API features, usage scenarios, and best practices.
  • Change Logs: Records of API changes over time, such as new features, bug fixes, and deprecations.
  • Glossary: Technical terms defined in the API documentation.
  • FAQ: This section contains frequently asked questions and answers concerning the API.

Documenting Best Practices

  • Be concise and clear: Use basic language and examples to keep the documentation as clear and brief as possible.
  • Use consistent formatting: To make the documentation easier to read and comprehend, use an uniform formatting style.
  • Keep it up to date: Update the documentation on a regular basis to reflect changes to the API.
  • Provide examples: The documentation should provide examples to help clarify any ideas.

Tools for API documentation

There are several tools available for generating and managing API documentation, including:

  • Postman: A tool for testing APIs that also includes documentation generation.
  • ReadMe: A platform for creating and hosting API documentation.
  • Swagger: An open-source tool for generating and maintaining API documentation.


Developing a RESTful API is a complex process that involves several steps. In this article, we have discussed the key concepts and best practices for developing RESTful APIs, including API design, API security, API performance, and API documentation. We have also discussed the tools and techniques that can be used to implement these best practices. By following these best practices, you can ensure that your RESTful API is secure, scalable, and easy to use. You can also use these best practices to improve the performance and reliability of your existing RESTful APIs.