Looking at the error rates, I wonder what happened at around 12pm?
(Screenshots: http://grab.by/7gJ4 http://grab.by/7gJ5 http://grab.by/7gJh)
The maintenance work has been completed. The datastore was in a read-only period between 12:02-12:45 for a total of 43 minutes. Some users reported two periods of 500 errors unrelated to datastore writes, but these issues should no longer be occurring.
On Nov 6, 12:01 pm, App Engine Downtime Notify <i...@google.com>