A failed upgrade left the world Twitter-less for several hours last night.
The service has now been restored, although users might be getting messages in a mixed-up order for an hour or two.
A message on Twitter's blog blamed the failure on "the failed enhancement of a new approach to timeline caching".
An update at 11.51pm Pacific Daylight Time warned that users might continue to get out of sequence or duplicate messages but promised the problem would be fixed soon.
At the time of writing Twitter is up and running fine. Top trending tweets include "Twitter Over Capacity" and "Stupid Twitter..." ®