What is a REST API?

REST APIs provide a flexible and lightweight way to integrate applications and are emerging as the most popular way to connect components in microservices architectures.

An API (Application programming interface) is a a set of rules and protocols that defines how software products and applications communicate with each other.

Let's visualize an API as a waiter in a restaurant. You the customer can be referred to as the client while the chefs in the kitchen can be called the Server.

Now the Waiter is a way or protocol through which you place your order (communicate) to the chef (server) and also get a response if any (your food perhaps).

If there are any errors, let's say the food isn't available. The chef will communicate to you through the waiter and so on.

This simple analogy can be applied to how software applications communicate.

Now that we have had an overview of how APIs work, What is a REST API and why do we use it?

What is a REST API?

A REST API also known as RESTful API is an API that follows the design principles of REST (Representational State Transfer) architectural system.

REST APIs are the most widely appreciated APIs and are preferred to other APIs like SOAP or XML-RPC because of the flexibility it offers to software developers.

It is also language agnostic, meaning that they can be implemented in virtually any programming language and they support several data formats.

The only condition in developing REST APIs is that they conform to the following REST design principles listed below:

1. Uniform Interface : This means that each request made from the client to the server should look alike no matter where that request is made from. The REST API should guarantee that the same chunk of data from the client belongs to only one URI (Unique Resource Identifier).

2. Cacheability : Resources being communicated via a REST API should be cacheable on both the client and server side of the application. Responses should also include information that tells the client if caching is available for that resource. This helps improve performance on the client side and scalability on the server side.

3. Client-Server decoupling : The client and server side of the application must be independent of each other. The only information about the server that should be known by the client is the URI of a requested resource. The client should not be able to interact with the server in any way. Likewise, the server shouldn't be able to alter the client, it should only be able to process the requested data via HTTP.

4. Layered system architecture : The calls and responses in REST go through different categories also known as layers. This means that the client and server may not connect directly with each other. There may be several channels in the communication loop.
   
   To this end, REST APIs need to be designed so that the client and server are not aware of the communication channel used(whether it's an end to end communication or through an intermediary between them).

5. Statelessness : REST APIs are stateless. Rather than relying on the server remembering previous requests, REST applications require each request to contain all of the information necessary for the server to process it. Server applications arent allowed to store any data related to a client request.

How does a REST API Work?

REST APIs communicate through HTTP(hyper text transfer protocol) to carry out database functions or operations like creating, reading, updating, and deleting information (also known as CRUD) within a resource.

In HTTP, there are five common methods that are used for communication, they are:

• GET: The get method is used to read or retrieve the representation of a resource in a database.

• POST: The post method is used to create new resources in the database.

• PATCH: The patch method is used to modify the data or information within a resource identified by a URI. This request only needs to contain the changes to the resource not the complete resource.

• PUT: The put method is used to update and modify the data within a resource identified by a URI. This request needs to contain the complete resource ie. if you want to change the username of a user, you'll need to provide every other information relating to that user resource.

• DELETE: As the name implies, the delete method is used to delete a resource identified by a URI.

The state of a resource at any particular instant is known as the resource representation and this information can be delivered to a client in several formats including JavaScript Object Notation (JSON), HTML, XLT, Python, PHP, or plain text.

JSON is by far the most used between software developers because it is readable by both humans and machines and it is programming language-agnostic.

Request headers and response headers, along with conventional HTTP status codes, are commonly used within REST APIs.

Request headers and parameters contain important identifier information like metadata, authorizations, uniform resource identifiers (URIs), caching, cookies etc.

Benefits Of REST APIs

1. Flexibility and Scalability : One of the most important benefit of REST APIs is the scalability and flexibility it offers software engineers. REST APIs can be scaled quickly due to the separation between the client and the server. Additionally, due to its flexible nature engineers can also easily integrate REST APIs without much added work.

2. Independence : In the architectural design of REST APIs, the client and server are independent of each other. This means that engineers can go on to work on different parts of the application separately.

3. Lightweight : One of the main benefits of REST APIs is that they follow HTTP standard, which means that they're format-agonistic and you can use XML, JSON, HTML, etc. Making REST APIs fast and lightweight. This feature is particularly necessary for mobile app projects, internet of things devices, and more.

Disadvantage of REST APIs

Flexibility : Yeah, you heard right FLEXIBILITY! Although it is a big advantage of REST API design, it also makes it easy to develop an API thats broken or/and performs poorly.

REST APIs are the most popular and widely used APIs in the world of software development . They are efficient, high-performing, consume less bandwidth, and are cost-effective.

That's a wrap, you can go ahead and start building your own APIs. While designing your APIs, you should make sure to take cognizance of your consumer's objectives and then build accordingly.

If you have any questions or suggestions, I'll be buzzing to hear from you in the comment section.

Happy coding 💫