> Note that just before I'd left they'd been investing in standing up AMS (I think) but had never successfully tested a significant failover

IIRC, AMS was/is just a new DC to replace or augment LUX, which has existed for some time as, among other things, a failover secondary for PDX. But yeah, intention and reality drifted, as they always do; I had heard a variety of reasons why automated, or even break-glass, failover to a DC on the opposite side of the planet wasn't a tenable solution for many workloads.

They're big on chaos testing, and definitely (very regularly) test whole-DC network partitions. I'd love to be a fly on the wall in the meeting discussing why this event was so different.