Sounds like a kill switch might not be that hard after all.

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Google may have taken this whole 'serverless' thing too far: Outage caused by bandwidth-killing config blunder
Engineers struggled to restore own packet-starved systems during four-hour SNAFU
By Shaun Nichols in San Francisco 4 Jun 2019 at 20:19

Google says its four-hour wobble across America and some other parts of the world on Sunday was caused by a bungled reconfiguration of its servers.

The multi-hour outage affected Google services including Gmail, YouTube, Drive, and Cloud virtual-machine hosting, and knocked out apps like Uber and Snapchat that rely on the web goliath's systems. During the kerfuffle, affected netizens noticed their connections to the G mothership were slow, unreliable, or in some cases down completely.

According to veep of engineering Benjamin Treynor Sloss on Monday, the problems began when Googlers tried to push new configuration settings to a handful of servers in one of Google's data center regions. Somehow, that update ended up also being applied to many other servers in several other regions, causing them to give up more than half their network bandwidth.

That in turn starved systems of packets, ultimately leading to services appearing to fall over or slow down for users.

"In essence, the root cause of Sunday’s disruption was a configuration change that was intended for a small number of servers in a single region," said Sloss. "The configuration was incorrectly applied to a larger number of servers across several neighboring regions, and it caused those regions to stop using more than half of their available network capacity. The network traffic to/from those regions then tried to fit into the remaining network capacity, but it did not."

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https://www.theregister.co.uk/2019/06/04/google_outage_botched_server/