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What is Reactive?

Reactive means reacting to changes in a timely manner or responding to changes in a timely manner.

Here, in the Reactive World, we can represent a change as an event. So we can also define Reactive as reacting to events in a timely manner. This change can occur on data or data elements.

Whenever a change occurs in our system, the system should react to those changes immediately in a timely manner. In the current world, users expect a response from an application (website, web application, mobile application, and so on) quickly and in a timely manner. If the system or application does not respond to the user (or customer) in a timely manner, the user will look for some other option and our application will lose its users.

In the Merriam Webster dictionary, Reactive means being readily responsive to a stimulus (check out https://www.merriam-webster.com/dictionary/Reactive).

In the Reactive World, a change is an event. In Reactive systems, we represent that event as a message. We will discuss why we need to represent an event as a message in detail in subsequent sections.