Twitter says that an outage yesterday wasn't, as rumored, caused by an overload from Olympic traffic.
The site was down from around 8.20am PT for a little over two hours. Users around the world were affected, although many were able to access the service via Twitter's mobile site.
Many observers suggested that the cause was the increased traffic triggered by the start of the Olympics today.
But, says Twitter, it was a problem within the company's data center: when one system failed, the parallel system designed to take over failed too.
"What was noteworthy about today’s outage was the coincidental failure of two parallel systems at nearly the same time," says VP of engineering Mazen Rawashdeh.
"I wish I could say that today’s outage could be explained by the Olympics or even a cascading bug. Instead, it was due to this infrastructural double-whammy."
Rawashdeh says the company is investing 'aggressively' to avoid the same situation in the future. But it will have its fingers crossed over the next few days, with a massive spike in usage expected as the Olympic Games start.
During the recent UEFA European Football Championship final, the site saw traffic of more than 15,000 tweets per second.
While Twitter was once notorious for its Fail Whale, outages are rather rarer these days. In June, users lost service for around two hours in an outage blamed on a cascading bug.