> Operators instead relied on logs to understand what was happening and initially identified elevated internal DNS errors. Because internal DNS is foundational for all services and this traffic was believed to be contributing to the congestion, the teams focused on moving the internal DNS traffic away from the congested network paths. At 9:28 AM PST, the team completed this work and DNS resolution errors fully recovered.

Having DNS problems sounds a lot like the Facebook outage of 2021-10-04. https://en.wikipedia.org/wiki/2021_Facebook_outage