What happens when connection draining is enabled for a load balancer?

When connection draining is enabled for a load balancer, it ensures that ongoing requests to instances are allowed to complete before the load balancer stops routing new requests to those instances. This feature is particularly useful during maintenance or scaling activities when you might want to gracefully remove instances from service.

By allowing in-flight requests to finish, connection draining helps to prevent dropped connections and ensures a smoother user experience. Meanwhile, it effectively stops new traffic from being directed to instances that are marked as unhealthy or about to be taken out of service, thus protecting the overall performance and stability of the application.

This process is vital in environments where uptime and user experience are critical, enabling a balanced approach to maintenance and scaling without disrupting service. Connection draining thus helps maintain application stability while allowing for necessary changes or upgrades to backend instances.