Reactive system is defined in the reactive manifesto at http://www.reactivemanifesto.org/. The creators of the manifesto realized that with the change of technology, new system patterns will need to be developed in enterprise computing to leverage the new technology and yield better outcomes. The manifesto envisions systems that are:
- Responsive
- Resilient
- Elastic
- Message-driven.
The first three features are user values; the last one is more of a technological approach to get the values.
A system is responsive if it gives results in a reliable manner. If you talk to me, I will answer your question or, at least, tell you that I do not know the answer or that I was not able to understand the question. Better if you get the answer, but if a system cannot give that to you it is still expected to give something back. If you have past experience with client operating systems from just ten years ago and some old computers, you can understand this. Getting a rotating hourglass...