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we host things called hackathons. this is one or two night thing. come with all the ideas.kly and basically prevent all the cool new hacks that come out of it. liz: that is -- i want to go to one much those things. >> there is pizza and beer and stuff for sure. liz: how did you go about building servers that could hand ale billion members of facebook? that's incredible. by the way, think about this, all the pictures you yourself might put on your facebook page, seven years later, they're still there because of way servers support, handle and keep that stuff, right? >> yeah. obviously they have to be very reliable. but other big thrust was making them efficient's well. when you have that much infrastructure, it need to be really efficient because obviously the electricity costs and ongoing operating costs can be pretty overwhelming thick. so we took on this concept what we call vanity free design. basically strip out anything not doing something useful, right? if it is not helping you or photos or helping but get all the most relevant news feeds uniquely come bossed for you,