Application Programming Interface API

Application Programming Interfaces (API) – REST, SOAP, WEB API, Microservice. Easy 10 Min Read.

Picture of topictrick
An application programming interface (API) is a set of protocols that enables interaction between different applications or systems. APIs are generally divided into different categories such as private or public APIs. REST API, SOAP API, WEB APIs, Microservices are different format of APIs. The API business model has now become a source of revenue for companies.

Table of Contents

Application Programming Interface Introduction.

Welcome to today’s article on “Application Programming Interface (API)”. You’ll learn the basic concept and the complete life cycle of APIs. in addition, you will also get the basic overview of web API, microservice, REST API, SOAP API, APIs category and how APIs works. Let’s begin our tutorial with an overview of application programming interfaces (APIs).

What is an API?

An acronym API stands for the Application Programming Interface. It’s a special class of software or a set of protocols or set of routines that enable interaction between different applications.

APIs are available on all most all platforms and support all devices. These are generally small server-side application, deployed in the form of a micro-service and can be hosted on any platform.

The application programming interface enables the interaction between the application hosted either on the same platform or on a different platform. It also enables the secure exchange of the data between different systems.

All APIs are not Web Services. However, all Web Services are termed as APIs.

APIs help in creating the decoupled and reusable building blocks that can be used in software development. The below API flow diagram highlight the basic architecture of an API.

Application programming Interface Architecture
Application programming Interface Architecture

Millions of mobile users everyday make billions of API calls to book their flight, transfer payments, book taxi, etc. and everything is possible due to APIs. API is driving the world and APIs have become an irresistible product for a business house. Here, are some example of tops used APIs in 2020:

How Application Programming Interface Works?

We have billions of smartphone users across the globe and everyone is using different mobile apps to order food, book taxi, transfer payment, booking flights, etc. All these applications call APIs in the background to complete the user request. Now, let’s try to understand how the application programming interface (API) works with a banking mobile app.
Let say you want to check your account balance via banking mobile app. The process of getting your account balance is a two-step process.
  • Open your mobile app and type your login credentials.
  • As you click on login, the mobile app use API service to initiates a session with your banking application to authenticate your credential and get the account balance.
Mobile apps are only acting as an interface to access data from a remote system via APIs. The application interface layer will call either a REST API or SOAP API or probably a microservice depending on banking application architecture to get your account balance.
The received API response will be visible on your mobile screen. The following figure showcase how application programming interface works in real-time.
Application programming interface
Application programming interface

What are key benefits of Using APIs?

An application programming interface (API) enables enterprises to reach out to new audiences. The major factor that leads to the tremendous growth of APIs is the mobile phone.
Mobile applications are dependent on APIs to exchange data with the host systems. Thus, the growth of mobile apps would lead to the growth of APIs. The number of public APIs is growing day by day, according to ProgrammableWeb in 2005 there was only very few public APIs. But, this number grows to 17,000 approx by 2017 and the number is still growing at a staggering rate.
The following are the benefits of using APIs.
  • APIs are fairly simple and easy to use. Being a programmer you’re not required to build an application right from scratch. You only need to build logic to consume data return by API services.
  • APIs support various data exchange format such as JSON, CSV which is fairly easy to parse by the applications.
  • APIs can be used to expose legacy data to the outside world in a secure way.
  • APIs can be used to automate work, in-fact they can scale the service on demand.

What are different types of API?

By now, you’ve understood the meaning of APIs and their practical use in various areas. Now, let’s concentrate on the different types of application programming interfaces (API). Generally, there are three different types of APIs category:

topictrick social strategy

Ownership Based APIs

Based on the access level, APIs are further divided into Public API and Private API. Public APIs can be accessed by anyone without any restriction. However, private APIs are designed and used internally within the application or organization.

topictrick communication

Communication Based APIs.

The next API classification is based on communication levels. These APIs are classified as high-level API in the form of REST APIs and system-level APIs in the form of SOAP APIs. System-level Apis generally support more system-level functions.

topictrick advertising

Web Service Based APIs.

The last category of APIs is web services API, these are generally used a different set of protocols and data formats. The Web services are divided into four types i.e. SOAP, JSON-RPC, XML-RPC, and REST APIs.

The below diagram showcases the different types of API category.

applicaiton programming interface types
applicaiton programming interface types

You might be wondering that REST APIs and WEB APIs are two different concepts. But, you will be surprised to know that both the REST API and WEB API are two sides of a coin. They are very similar in functionality and has a minor difference. Let’s go them one by one.

What is a Rest API?

The term REST stands for Representation State Transfer. It’s easy to learn and flexible to use and you don’t need any special tools. Roy Fielding developed the REST API in the year 2000.

He and his team keep the design of the REST API simple and easy to use. It was designed to overcome the shortcoming of SOAP APIs.

The REST APIs provide four methods GET, POST, PUT, and DELETE.
    • GET Method – is used to retrieve the record.
    • PUT Method – is used to update the record.
    • POST Method – is used to insert the record.
    • DELETE Method – is used to delete the record.
REST APIs are fairly simple and easy to use. You can receive the output of request either in JSON or RSS or CSV depending on your application. Last but not the least, they use URL for communication.


A web API is a web interface for any external or internal application. In laymen terms, it’s a point where two applications meet and exchange data by using a common set of protocols.

Web APIs are generally known as remote APIs that use the HTTP protocol for communication. In the below example, the mobile application is a consumer of the API hosted on a webserver. The back-end server will act as provider because it fulfils the request of a web server.

The back-end server will act as a provider because it fulfils the request of a web server or mobile apps. Every day millions of mobile apps, websites, or any third party software call various APIs to consume expose data.
Application Programming Interface act as a building block in the development of any new application. The programmer can use APIs to consume data rather than writing data access code from scratch.
What is a Web APIs
What is a Web APIs

What is a SOAP API?

The term SOAP stands for Simple Object Access Protocol. It is a standard web service protocol and it was the only means of communication between application before the development of REST.
Microsoft designed the SOAP API in 1998. SOAP only supports XML data format/message for communication. SOAP APIs are bit complex, even for small requested you need to wite huge chunk of code. Having said that SOAP APIs supports a more rigid set of messages than REST APIs.
SOAP is a platform, language and protocol neutral and it supports WS* standards and has built-in error handling. SOAP API is good for distributed environments.
SOAP API is still preferred when it comes to sharing sensitive transaction details with the third party due to its ACID compliance. For example Banking application, flight booking applications etc generally used SOAP APIs.

What is a Microservices?

Microservices is another popular termed of the API terminology. In layman term, microservices is a modular, self-contained, independent service or functionality. Microservice generally does not depend on a feed from any other microservice or API.
However, it can consume feed from other microservices. Microservices are generally used to split a large application into a small set of more logical manageable groups for example payment microservice, reporting microservice etc. Finally, the group of microservice is exposed to REST APIs.
In below mention example the application is split into three different microservices. The payment microservices, reporting microservice, ML microservices are exposed to REST API.
Microservice Architecture Overview e1588274513486
Microservice Architecture Overview e1588274513486


In today’s IT, paradigm APIs have become a necessity for any organization to expose data to third-party or to consume a partner’s data. Designing and building a robust APIs is important for any software application. A well thought and robust, APIs design enables applications to integrate with the external environment. It also provides an edge to an organization in changing the business landscape.
The application programming interface has a life cycle like any other software product. The application programming interface life cycle is essentially divided into five phases:
topictrick interface

Design Phase.

The application programming interface begins with a well thought robust design. The design should be leak-proof and follow enterprise architecture guidelines. In this stage, you prepare the resources and operational requirements along with the business case scenarios.

topictrick coding

Development Phase

The next phase is the development phase. In this phase, APIs business logic is developed as per business requirements. This phase is quite important because in this phase design is transformed into code.

topictrick testing

Testing Phase

In the third phase in testing, in this phase, the APIs logic is tested as per business requirements. You test the API to ensure that the quality and performance of the API is robust and to avoid any hiccups in productions.

topictrick connection

Deployment Phase

The fourth phase is to deploy the tested API into secure production environments. Then new API can be accessed via any third-party or inhouse applications.

topictrick performace

Retiring or Deprecating Phase

The final phase of the API life cycle involves retiring or deprecating the API. In this phase, the older version of APIs is retired including support for the corresponding API.

What Is the API Economy?

The API economy is not a new concept, in fact, is being around since the last couple of years. In layman terms, the API economy is the process of monetizing the API service.
Big tech giants such as Microsoft, Google, Amazon has developed various service and expose them to the outside world. Many global banks have developed payment gateways and clearing system which can be accessed by APIs.
Thus, the API business model has now become a source of revenue for companies. More and more companies are now using APIs as a business strategy.

Do you need an API?

Well, good question. There is no doubt the APIs add value to the Business. Businesses look at application programming interface (APIs) to reduce costs, open their system to third-party, or monetize services.
In-fact organization that supports APIs architecture has an edge over its competitors. However, the power of APIs cannot be ignored, it can help an organization to reduce cost, tap new opportunities.
APIs are not mandatory but now it has become an integral part of business strategy.

Topictrick: Application Programming Interface Video

This tutorial is associated with a video so that you can have a better understanding of application programming interface (API) terminology.


Finally, this mark and end to today's article on Application Programming Interface (API). In this article, you learn about APIs, SOAP API, REST API, Web Services, Microservices. You also learn how is API is generating revenue for big tech giants. Please do share your feedback and subscribe to our the youtube channel for more such videos.