This sounds very much like what caused Amazon’s last S3 outage. A configuration change applied to more servers than expected. It’s unfortunate to see Google did

This sounds very much like what caused Amazon’s last S3 outage. A configuration change applied to more servers than expected. It’s unfortunate to see Google didn’t take action to prevent this after it happened to AWS and instead waited until it happened to them before realizing they need to put in safeguards against this. Looking forward to the final write up on this with more details, but at first glance the cause looks just like S3’s last outage.