If your application has lots of users accessing the system simultaneously, then obviously a single server cannot handle all the traffic. It will slow down and crash. Therefore, we need to deploy the application on multiple servers and then distribute the traffic equally between them.
To distribute traffic between servers, we need to use something called a load balancer. A load balancer is a server that sits in front of the application servers. The client communicates with the load balancer instead of the application servers, and instead of handling the request, the load balancer forwards it to an application server; when the application servers sends the response, it sends the same response to the client.
As a load balancer doesn't actually process the request, it can handle many more requests than an application server. Obviously, a load balancer cannot handle unlimited requests, so we can use multiple load balancers. When we use multiple load balancers, the traffic...