Understanding the reactive pattern

Today, the modern applications must be more robust, more resilient, more flexible, and better positioned to meet the requirements of the organizations, because, in the recent couple of years, the requirements for applications have changed dramatically. As we have seen in the last table, 10 to 15 years ago, a large application had 10 server nodes, the response time taken to serve a request was in seconds, we required a couple of hours of downtime for maintenance and deployment, and the data was in gigabytes. But today, an application requires thousands of server nodes, because it is accessed by multiple channels such as mobile devices. The server responses are expected within milliseconds, and the downtime for deployment and maintenance is near to 0%. Data has been increased from terabytes to petabytes.

Ten-year old systems cannot fulfill the requirements of today's applications; we need a system that can fulfill all user's requirements either at the application...