Just In Case: Facebook's "Nuclear Option"

The Facebook infrastructure team has blogged about the challenges involved in its recent launch of usernames, which allow Facebook users to personalize or brand their profile URL. With more than 200 million users and a single login page URL, the launch of usernames was "unique in its preparation and potential for trouble," Facebook's Tom Cook writes on the Facebook engineering blog.

Facebook VP of Technical ops Jonathan Heiliger discussed some of the launch management strategies at last week's Velocity 2009 and Structure 09 conferences, including the use of a "dark launch" and the decision to go live with the username feature at a period of low traffic.

But Cook digs into some interesting "just in case" scenarios the Facebook team developed to manage a variety of traffic and web site load scenarios. "Facebook comprises hundreds of interlocking systems, although to users it's presented as a simple web page," he writes. "Throttling back the behavior of certain facets allows us to lighten the demand on our infrastructure without compromising major site functionality."

Facebook was prepared to take drastic steps if the username land rush challenged its capacity.  

"In the event that Facebook became overwhelmed with traffic and suffered performance problems as a result, we also prepared for what we called 'Nuclear Options' such as cutting off nearly all the functionality on the Profile page, turning off Facebook Chat, and completely disabling the Home page," Cook writes. "Any of these options were an absolute last resort to keep the site functional as they would have resulted in a severely degraded user experience."

None were needed, as Facebook smoothly handled more than 200,000 username registrations in the first three minutes, and more than 1 million in the first hour. "Through the entire launch we had no issues handling the additional load," Cook reports.