At times of heavy load for more on how Twitter manages its capacity challenges, see Using Metrics to Vanquish the Fail Whale. Twitter's last major downtime event was a 3 hour, 40 minute outage on August 6, when Twitter was among the social networking sites targeted by an electronic attack, which prompted the service to beef up its network defenses. While some Twitter-watchers continue to debate whether its growth is continuing, co-founder Ev Williams posted Jan. 12 that "across all metrics that matter, yesterday was Twitter's highest-usage day ever. (And today will be bigger.)"