An Application Programming Interface (API) is a set of rules and protocols that enables different software applications to communicate and share data with each other. APIs offer a structured way to extract and share data between applications or software systems. This can happen within or between organizations. A meticulously designed API serves as the cornerstone for the success of software applications and platforms.
More simply, an API works by defining functions or procedures that enable both the creation and management of requests and responses between software systems or applications. To do this, we have to specify the following:
APIs, by abstracting complexity and standardizing communication, inherently promote modularity in software design. This approach breaks down systems into manageable, independent components. Developers, focusing solely on API inputs and outputs, can leverage one module at a time and treat them as black boxes. This not only simplifies integration but also reduces development challenges.
The benefits extend beyond simplification. A modular design, underpinned by APIs, ensures greater software maintainability and scalability. Any updates or replacements in a module can be executed without disrupting the entire system, provided the API contracts remain consistent. This framework encourages more adaptive and resilient software solutions, catering to evolving requirements.
An API operates on the fundamental principle of request-response communication, acting as a bridge between different software modules or applications. For instance, in a typical scenario, it connects a front-end application, known as the client, and a back-end system, known as the server. The client is what users interact with, while the server handles the underlying logic and data storage. The API ensures that the client and server can exchange data and commands.
For example, consider two microservices in an online shopping platform: one handles inventory, and the other processes payments. When a user tries to purchase an item, the payment microservice needs to check if the item is in stock. Here, the payment microservice acts as the client, sending a request via the API to the inventory microservice (acting as the server). The inventory microservice then checks its database and responds via the API, letting the payment microservice know if the purchase can proceed.
Figure 1: An example of an API
APIs have evolved to cater to the dynamic demands of the tech landscape. As devices proliferate, real-time data becomes paramount, and application needs diversify, developers are presented with a myriad of API types, each designed to serve specific purposes.
Different API types like Representational State Transfer (REST), Simple Object Access Protocol (SOAP), Remote Procedure Calls (RPC), GraphQL and WebSockets emerged to cater to these varied needs. In selecting an API type, developers weigh the advantages and challenges of each approach against their project's specific requirements, aiming to find a balance that best suits their application. Let's delve deeper into these API types, outlining their benefits and shortcomings: