Twitter released an explanation and apology for the service outage on Thursday.
The company said the root of the problem was a failure of two parallel systems at its data center.
Twitter released this statement on its blog:
We are sorry. Many of you came to Twitter earlier today expecting, well, Twitter. Instead, between around and , users around the world got zilch from us. By about , people who came to Twitter finally got what they expected: Twitter.
The cause of today's outage came from within our data centers. Data centers are designed to be redundant: when one system fails (as everything does at one time or another), a parallel system takes over. What was noteworthy about today's outage was the coincidental failure of two parallel systems at nearly the same time.
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. We are investing aggressively in our systems to avoid this situation in the future.