What is an Application Programming Interface (API)

Every person uses a mobile application and web application that uses API for their front-end or back-end process. But do you know what API is?

What is an API?

Application Programming Interface (API) is software that allows communication between two software applications. Technically, what an API does is that it receives a message from one and tells the other, and responds.

Imagine you are in a restaurant; you have a list of food items on the menu, but you want to have specific items and the kitchen as a system that can provide you with all the requests you make.

But wait, who will tell the kitchen what you want and how you like it? Then Waiter will take your order and convert this kitchen to get what you want.

The API is just like the waiter in the restaurant that will take your request from your end and send it to the DB/server and take the response back to you.

Let me make it more clear with some real-life examples.

I’m sure you are familiar with the airplane ticketing system; just like the restaurant, you have multiple options like different cities, departure and return dates, and many more. If you are booking an airplane ticket from their website, you put the date, city, and other variables which in terms access the website database to check the seat availability and its costing.

But what if you are booking through online travel or ticket service providers like Paytm, Expedia, MakeMyTrip, or something similar?

In that case, those online service providers had to connect with many airplane databases using API. It will ask the online travel service providers to get the information destination, date and time, baggage option, etc. Then API will take the response from the airline’s database to your request and deliver it right back to the travel service providers.

How does an API work?

API lets your product or service communicate with each other or different products or services without letting them know their implementation process. It will provide you with simplicity and flexibility and provide an opportunity for innovation.

Sometimes API is considered a contract between two different parties; if 1st party sends a specific request, this is how 2nd party will respond.

Types of API

When talking about the accessibility and usability of API, many would agree to categorize the API on four different levels.

• Open API
• Partner API
• Internal API
• Composite API

Open API

Also known as Public APIs, they are available to any developer. It has minimum authentication measures, which in terms restricted their shared data. It helps share the data more freely and openly with any business owners.

For Example, Many web developers use Google Map API to integrate the map on their web app or website to provide easy navigation to their audience.

Partner API

These types of APIs are shared externally only with that business that already has a relationship with the API-providing company. And limited access is only provided to the authorized users with official licenses. These APIs would offer greater control over the resources and how they can use them.

For instance, Pinterest API will ask you how you would like to use the data and resources provided before granting you access to their API.

Internal API

These APIs are shared internally within a business to streamline the data and resources sharing between the departments and teams and can’t be shared with third parties.

Using Internal API would be a more efficient, secure, and traceable way to transfer data within the business.

Composite API

The developer uses the Composite API to set numerous automatic responses from different servers. It combines various APIs to help developers bundle calls or requests and receive one unified response from servers.

They reduce the number of total APIs events and even result in less server load with fast loading system.

Types of API Architectures

We also have to understand the types of APIs based on an architecture that defines what information it will share and how it will share the data with the clients.

The most common types are -

• Representational State Transfer (REST)
• Remote Procedural Call (RPC)
• Simple Object Access Protocol (SOAP)

Representational State Transfer (REST)

It is a set of Guidelines for scalable, lightweight, and easily accessible APIs. A rest API is an API that follows all the guidelines and uses them for transferring data from server to client.

A few guidelines are -

• Client-Server Separation- All the Client-Server Interactions must be in the form of a request from the clients followed by a response from the server.
• Stateless- All the Client-Server interactions are different from one another. The server will not store any data or requests made by the client.
• Uniform Interface- All the customer requests and company responses must use HTTPS as Communication Protocol while ensuring the compatibility between clients and servers.
• Layered System- Client’s Response and Server Response must always be the same, even when passing through the client and the APIs.
• Cacheable- every request and response must be cacheable, eliminating the need for client-server interaction.

Simple Object Access Point (SOAP)

It is a protocol for transferring data across networks with XML as a format. Its primary function is to define how messages should be sent and what it includes while making them more secure than REST APIs.

SOAP is used for internal data transfers that require high security, and it works over any communication protocols.

Remote Procedural Call (RPC)

It is the most simple API Architecture among SOAP and REST, as it invokes the process of data transfers.

It will either employ JASON or XML to share the data, as RPC is a simple and easy way to execute code on any remote server. RPC APIs are limited in their security and capabilities, so they are not well used by developers.