Net workers' nightmare came true. Lesson from April 21 outage of Amazon.com

The incident summary of April 21 outage of Amazon.com has been published for a while. It reminds me some typical nightmares of an Net worker like me.

The "prelude" of that incident was because of network execution error, as this:

..... The configuration change was to upgrade the capacity of the primary network. During the change, one of the standard steps is to shift traffic off of one of the redundant routers in the primary EBS network to allow the upgrade to happen. The traffic shift was executed incorrectly and rather than routing the traffic to the other router on the primary network, the traffic was routed onto the lower capacity redundant EBS network. .....