An API may be defined as a function or script written to help several applications interact with each other. Having said that, APIs have become tightly linked with IoT because they allow your devices to be safely connected to external applications, such as sending orders to your car or turning the lights on at your home. This is why it is important for the APIs to be designed in a proper manner that is secure, flexible and scalable.
APIs can be used by an external application requiring authentication through a “key”, they can be 100 percent free and openly accessible, not needing any form of registration or authentication. With the assistance of APIs, a single application can be running and utilizing several other programs together, even if each program was built with different technologies, this is thanks to the unified architecture used that is called REST.
Unstructured data may be stored as objects, semi-structure goes to MongoDB, Cassandra. The more orthodox and structured information goes to SQL, MySQL, etc. As an engineer, it is difficult to manage APIs uncovered by all these information sources. To incorporate one unstructured, one semi-organized and one organized data set in your application you need to manage at least three proprietary APIs. This reduces your efficiency and makes you more inclined to committing mistakes since you are mixing and matching exceptionally heterogeneous API into your applications.
Imagine driving through the streets of a highly populated city. However, in that city, on the roads, there aren’t any lane dividers, crosswalks, or signals. That would be a complete chaos. This is analogous to the case with IoT. There should be a high leverl architectural design standardizing the flow of information to make the interaction among the devices truly meaningful. This is why REST APIs have been created and used.
So as a summary, APIs in IoT, as in the context of IoT many devices of different hardware and technologies will be communicating with each other, and thus we need a standardized way to make the flow of information meaningful irrespective of the programming languages, operating systems and hardware used by each node. This is why there is a need for a careful design of APIs as they will be the gateway to the world to communicating with important devices, and also they will be the basis of the system determining the level of scalability that it can achieve.