Application Programming Interface

API stands for Application Programming Interface, which is a software intermediary that allows two applications to communicate with each other using a set of definitions and protocols.

In contrast to a user interface, which connects a computer to a person, an application programming interface connects computers or pieces of software to each other. It is not intended to be used directly by a person (the end user) other than a computer programmer who is incorporating it into the software. An API is often made up of different parts which act as tools or services that are available to the programmer. A program or a programmer that uses one of these parts is said to call that portion of the API. The calls that make up the API are also known as subroutines, methods, requests, or endpoints. An API specification defines these calls, meaning that it explains how to use or implement them.

One purpose of APIs is to hide the internal details of how a system works, exposing only those parts a programmer will find useful and keeping them consistent even if the internal details later change. An API may be custom-built for a particular pair of systems, or it may be a shared standard allowing interoperability among many systems. APIs let you open up access to your resources while maintaining security and control. How you open access and to whom is up to you. API security is all about good API management, which includes the use of an API gateway.

Also check:- Waterfall Model(SDLC)

API architecture is usually explained in terms of client and server. The application sending the request is called the client, and the application sending the response is called the server. So in the weather example, the bureau’s weather database is the server, and the mobile app is the client.

Different types of APIs

Open APIs

An open API also refered as a public API is a publicly available application programming interface that provides developers with programmatic access to a proprietary software application or web service. Open APIs are published on the internet and shared freely, allowing the owner of a network-accessible service to give a universal access to consumers.

Open APIs can be designed in a variety of different ways, but the main priority of any open API is to be easily consumed and accessed by as many different clients as possible. Once an API is made public, it is difficult for an organization to control who uses the API and how they use it. As a result, API management must be taken seriously; otherwise, issues can arise in terms of customer satisfaction.

Partner APIs

Partner APIs are shared externally, but only among those who have a business relationship with the company providing the API. It is consumed by partners of an organization, meaning that there is an established relationship and some framework (often some form of contractual agreement).
Partner APIs are technically similar to open APIs, but they feature restricted access, often controlled through a third-party API gateway.

Internal APIs

Internal APIs are used by several companies to help them become more efficient in different aspects such as product development, HR and customer service. They exist on the company side of the Line of Business, in what could be considered the “back end” of the company, with no external exposure to customers, and no monetization. They are the usage of APIs purely as tools to make work more efficient. Private APIs allow developers to work efficiently by providing a centralized pool of internal software resources. Developers can use these resources to build multiple, varied applications and products which are later accessed by the public. This streamlines development and reduces resource-load, allowing the company to provide more services and products to customers.

Composite API

Composite APIs combine multiple data or service APIs. They are built using the API orchestration capabilities of an API creation tool. If you need data from different applications or data sources, you would use a composite API. Alternatively, you can use a composite API to set off an automatic chain of calls and responses without requiring your intervention. A composite API provides a design solution that is more efficient for the client. Instead of five or more requests, there is only one. Rather than parsing five or more responses, all the necessary data is passed at the end of the sequence.