A Look Behind The Curtain At Facebook's Optimization Efforts

Facebook is big. Really big. So it comes as little surprise that every tweak made to the site (like the subtle change to the header a few days ago) can have a pretty substantial impact on the way people use the social network. Earlier this week Facebook’s Engineering team posted a note written by intern Zizhuang Yang, who has spent the summer researching how changes in things like load time can affect users. Yang writes about three main experiments he conducted over the last few months, including one involving overall site speed and two in the way pages load, and the results are quite interesting.

The first experiment examined how Facebook users would respond to a general slowdown. Yang found that regardless of site speed, users spend around the same amount of time on Facebook. That might sound like good news (at least they don’t get frustrated and leave immediately), but it means that if the site is running slowly users are going to be seeing fewer pages in the same amount of time, which Facebook obviously doesn’t want. So — no surprise here — Facebook is striving to make the site as fast as possible.

The second experiment involved the order in which items on the page should load. Yang writes that Facebook has been internally debating whether the page should display everything as quickly as possible, even before some necessary scripts to actually interact with the site have loaded, or to show a white page until everything is good to go and then render it all at once. Yang writes, “In all groups of users, keeping the page blank resulted in lower usage statistics. Thus the debate was resolved.” So if you’re ever on Facebook and you find that a certain button isn’t working for the first second or two after a page loads, this would explain it.

The third experiment involved loading stories in the News Feed. Regular Facebook users have likely noticed that the site will automatically fetch more News Feed stories as you scroll down the page. This feels like a nifty new feature, but it was actually designed by Facebook to cut back on load times — News Feed used to show 30 stories at once; now it loads 15 at first and only shows the next 15 if you scroll down the page. What Yang found, however, is that when people do scroll beyond the initial 15 stories they’re shown, they’re happy to wait the extra second or two for 30 new stories to load, which results in a signifiant boost in engagement. This makes perfect sense — if I’m actively reading through the News Feed (as opposed to just seeing it because it’s Facebook’s home page) it’s because I’m killing time or trying to catch up on my friends’ past posts. The more stories shown during this ‘catch-up’ time, the better.

Also interesting to note is that Facebook seems keen to put its internship program in the public eye — just last week the site’s blog included a post from an intern who build the Facebook Pages to Twitter syndicator, and now we’re seeing the fruit’s of another intern’s summer experiments. This may well be part of the company’s plan to attract new talent during its recent hiring spree.