Google compute engine (GCE) was down globally for 18 minutes on the 11th. The usual culprit of configuration error was present but there was also a series of bugs that combined together to propagate a bad configuration into production.
It’s fascinating how small things combine to wreak havoc on large scale systems. Google is constantly testing so I imagine theses bugs have been quietly waiting in edge case land until random chance brings them together. With enough scale and complexity, the improbable becomes probable.