Facebook engineering team explains magic behind 10th anniversary videos

What might be the most impressive fact about Facebook's "Look Back" videos is that engineers only had a month to build a project that could scale and account for more than a billion users.
Written by Rachel King, Contributor

When Facebook celebrated its 10th anniversary in February, the social network treated its user base of more than a billion worldwide to special "Look Back" videos, one-minute long compilations of each user's posts and photos dotted out his or her's Facebook history.

But given that the Menlo Park, CA-headquartered business supports more than a billion users--and steadily counting--worldwide, not everyone was going to be satisfied, no matter how much Facebook engineers worked to ensure each and every video was personalized at some level.

Naturally, there were going to be some hits and misses, and post-viewing gripes and sentimental tears alike were shared on Facebook feeds for the following few days.

Unfortunately for me (or Facebook maybe, but really it's not a big deal), my own clip reel was a bit of a dud as none of the previous status messages or photos displayed were particularly memorable.

Nevertheless, that didn't stop me from watching it, which is likely all that Facebook wanted in the end.

The Facebook engineering team revealed some traffic stats on Thursday, admitting that, while they only expected 10 percent of users who actually watched these anthologies to share them, 40 percent of viewers ended up doing so.

Here's a rundown on some more results for Facebook's "Look Back" videos:

  • Not every user generated a video, but quite a few still did. Over 720 million videos were generated, with nine million videos rendered per hour.
  • This accounted for over 11 petabytes of storage used, surpassing 450 Gbps of outgoing bandwidth at peak and 4 PB egress within days.
  • More than 200 million people watched their Look Back movies within the first two days, while more than half shared their movie.

But what might be the most impressive fact about all of this is that Facebook engineers only had a month to build the project that could scale and account for each individual user.

The full details were published on Thursday for those who want to understand the magic behind this challenge, requiring the work and collaboration of approximately 30 internal teams.

Facebook engineers Alexey Spiridonov and Krish Bandaru revealed further that it wasn't until a few days before the official anniversary when the videos would launch on February 4 that engineers had a ready product.

With the initial setup in place, we tested the end-to-end pipeline with a prototype of the Look Back feature on about 150 employees. We continued to secure more capacity for the feature, and the team made hourly code changes and re-rendered videos to ensure that the software worked consistently and reliably for everyone. On January 24, we launched the Look Back videos internally to all Facebook employees. While there were still some bugs at this point, the feedback on the feature was overwhelmingly positive, and more people pitched in to help scale it.

Spiridonov and Bandaru added that the final product was ready to ship on February 3, just in time for the birthday bash.

One can only assume how many people pulled all-nighters to complete such a project on a tight timetable and deadline -- something to think about before posting an off-the-cuff frustration to your Facebook feed. Maybe it will come back to haunt you -- or just annoy you -- 10 years from now.

Image via Facebook

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