Explain use case for connection draining?

To ensure that a Classic Load Balancer stops sending requests to instances that are de-registering or unhealthy, while keeping the existing connections open, use connection draining. This enables the load balancer to complete in-flight requests made to instances that are de-registering or unhealthy.

The maximum timeout value can be set between 1 and 3,600 seconds on both GCP and AWS.