AS automatically adds instances during demand spikes and reduces instances during demand lulls. You must ensure that access traffic is distributed to all instances.
After ELB is enabled in an AS group, AS automatically associates the instances newly added to the AS group with a load balancing listener. ELB automatically distributes access traffic to all instances in the AS group through the listener, improving system availability. If multiple applications are running on each instance in the AS group, you can add multiple load balancing listeners to the AS group to listen to each of these applications, improving service scalability.