Almost four hours after Twitter came back to life from its terrifying Thursday outage, the company offered a bit of an explanation as to what happened, though it's not very enlightening. Apparently two parallel systems failed within Twitter's data centers at the same time, meaning there was no backup for whatever was broken, and the service stopped working. But the Twitter blog post by engineering vice president Mazen Rawashdeh does not explain which system crashed, or why. The going speculation, explored most thoroughly by Tech Crunch's Sarah Perez, was that a deluge of tweets by those excited about the start of the Olympics overloaded Twitter's systems. But Rawashdeh said the Olympics had nothing to do with it:
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.
So for now the best explanation of what went wrong is still the mysterious one users got when they tried to log on: "Twitter is currently down for <%= reason %>." It's nearly as enlightening as Twitter's actual explanation, and a whole lot funnier.