Spikability - An Application's Ability to Handle Load
blog.iron.io
blog.iron.io
edit: "And you can launch more servers to eat away at the queues if they keep growing." sounds a lot like autoscaling to me. The graph is misleading.
Regarding auto scaling, it is scaling your worker servers to work down the queues, but it is not as urgent/critical as auto scaling your app servers if they had to handle the load.
In most web-apps there is exactly one user-initiated task that can be deferred: sending e-mail. Last time I checked my "spikability" was not bound on sending e-mails.