I did see this article indicating they had somehow invalidated their cache in a botched deployment of changes - https://www.facebook.com/notes/facebook-engineering/more-details-on-todays-outage/431441338919/

On Thu, 14 Mar 2019 at 06:18, Mike Hammett <nanog@ics-il.net> wrote:

So what happened at Facebook today? I saw one article quoting Roland saying it was a route leak, but I haven't seen any other sources that aren't just quoting Roland. Usually there are a few independent posts out there by now.

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Mike Hammett
Intelligent Computing Solutions
http://www.ics-il.com

Midwest-IX
http://www.midwest-ix.com