Vendor lineage
Dyn - managed DNS, and the day it went down
Managed DNS and dynamic DNS provider, later acquired by Oracle.
Dyn provided dynamic DNS and managed authoritative DNS, and was acquired by Oracle. It is on this timeline for the architectural lesson its 2016 outage taught the rest of the industry.
A distributed denial-of-service attack against Dyn's infrastructure made a long list of major services unreachable at once - not because those services were down, but because the names that pointed at them could not be resolved. The applications were healthy and the internet could not find them.
The lesson generalised beyond one company: authoritative DNS is a single point of failure that does not look like one on an architecture diagram, because it is drawn as a lookup rather than as a dependency. The response across the industry was secondary providers and multiple authoritative services, which is a design decision made in the shape of a bill.