How Facebook's Safety Check Works
highscalability.com
How Facebook's Safety Check Works
1–10 of 52 posts
Re: How Facebook's Safety Check Works
#2A longer, more involved article from late September has a bit more information: http://highscalability.com/blog/2015/9/28/how-facebook-tells...
>If a friend is in the same area then a push notification is sent asking if they are OK.
One thing that I'd like to understand is how "area" is defined. The limiting factor is, of course, finding out something has happened, but someone at Facebook has to draw a border that encompasses everyone at risk but minimizes those out of harm's way. An earthquake is almost easier - there's (relatively) rapid data on the epicenter and size - but in an event and place like Paris, there have got to be some hard calls made in real time. Who are the people and teams involved there, and how do they make those decisions? I'd love to see that.
Re: How Facebook's Safety Check Works
#3> The average distance between any two of Facebook’s 1.5 billion users is 4.74 edges
Pretty crazy to think about.
Re: How Facebook's Safety Check Works
#4Here's the video from @scale that explains it if you are interested: https://www.youtube.com/watch?v=ptsCWGZW_P8
Re: How Facebook's Safety Check Works
#5A longer, more involved article from late September has a bit more information: http://highscalability.com/blog/2015/9/28/how-facebook-tells... >If a friend is in the same area then a push notification is sent asking if they are OK. One thing that I'd like to understand is how "area" is defined. The limiting factor is, of course, finding out something has happened, but someone at Facebook has to draw a border that en…
They probably are very generous - I'd imagine the entire country was defined as the "area". The system doesn't work very well if there's false negatives and people don't see it, and if someone sees it but shouldn't all they have to do is hit that they're OK.
Re: How Facebook's Safety Check Works
#6Hey everyone! FB engineer here who wrote the original code for this and gave the talk during @Scale 2015. There's a recording of our talk here:
https://youtu.be/ptsCWGZW_P8?t=333
That's a bit more visual and easier to understand. At the end of the day its really just DFS with seen state and selective exploration :)
Re: How Facebook's Safety Check Works
#7A longer, more involved article from late September has a bit more information: http://highscalability.com/blog/2015/9/28/how-facebook-tells... >If a friend is in the same area then a push notification is sent asking if they are OK. One thing that I'd like to understand is how "area" is defined. The limiting factor is, of course, finding out something has happened, but someone at Facebook has to draw a border that en…
They probably are very generous - I'd imagine the entire country was defined as the "area". The system doesn't work very well if there's false negatives and people don't see it, and if someone sees it but shouldn't all they have to do is hit that they're OK.
Not quite @chipperyman573. A few points to make here:
-- Since we only have city-level location for most users, declaring the area isn't as hard as drawing on a map. We usually just select a number of cities, regions, states, or countries that are affected by the crisis.
-- We always allow people to declare themselves into the crisis (or out) in case our geolocation prediction is inaccurate. This means we can be a bit more selective with the geographic area, since we want to be pretty high signal with our notifications. We actually use notification click-through and conversion rates as downstream signals on how well a launch went.
-- For something like Paris, we actually just selected the whole city and launched. Especially with the media reporting "Paris terror attacks," this seemed like a good fit.
Re: How Facebook's Safety Check Works
#8A longer, more involved article from late September has a bit more information: http://highscalability.com/blog/2015/9/28/how-facebook-tells... >If a friend is in the same area then a push notification is sent asking if they are OK. One thing that I'd like to understand is how "area" is defined. The limiting factor is, of course, finding out something has happened, but someone at Facebook has to draw a border that en…
They probably are very generous - I'd imagine the entire country was defined as the "area". The system doesn't work very well if there's false negatives and people don't see it, and if someone sees it but shouldn't all they have to do is hit that they're OK.
France is a pretty big country. If you are in Nice, you are a nine hour drive from Paris. It would seem a bit silly to ask if you were okay, and not someone in Belgium who is much, much closer.
Re: How Facebook's Safety Check Works
#9> If you are in an area impacted by a disaster Facebook will send you a push notification asking if you are OK.
I guess that's great during an earthquake but can be terrible when you're hiding during a terrorist act.
Re: How Facebook's Safety Check Works
#10Incidentally that article implies that Facebook contstantly tracks your geo location even when you do not expressly check in.