Google says that it was high load on the internet giant’s Contacts server that caused the outages of last week. Users of Google Apps could not access their Google Contacts on September 24, from 10 AM to 11:30 AM EDT. Gmail contacts were also unavailable from 10 AM to 1 PM EDT. This also affected Google Voice, as it relies on Google Contacts.
According to the Google Apps team, the solution was to temporarily stop all requests to the Google Contacts servers. A banner was shown in Gmail that informed users of alternate ways of accessing their contacts, but this likely did not lessen withdrawal symptoms for those affected.
On September 25, Google explained that the increased server load was caused by a rare convergence of events. First, an error in a network data center caused additional load on the Contacts server. Also, it just so happened that the server was experiencing higher than average usage that day. Finally, an update to the Gmail platform unintentionally increased load on the Contacts server even more. If they keep this up, their uptime might fall below 99%... the horror.