50 people is a pretty huge team at Google to start with, there’s teams of <5 that support weird bits of core infrastructure that serve billions of users an hour.
Billions per HOUR seems quite a stretch there..
Unless you're discussing background processes on google's side
You may not get a notification every hour, but the phone still have to connect to Google APIs to check to know that.
You can say same thing about say location services, every phone if powered and connected to the internet would ping more than one an hour, more than billion devices are definitely online at any give time, not just Android phones, also every android TV, tablet, watch, and the hundreds if not thousands of other devices running GMS on top of AOSP .
There are probably few other APIs in GMS that would ping at least once an hour each device that is powered on, perhaps things like NTP for timing alerts or Emergency Alerts etc.
You may consider them "Background Services" , most of them however have some foreground UI if they need to, and users will notice if they don't work
Something like DNS or BGP is going to have a tiny team and a huge impact. Load balancers probably has a bigger team, maybe 10-20 engineers, and almost everything goes through load balancers. And that's just the things that are easy to enumerate. I can think of lots of small teams when I was at Yahoo that worked on bits of software that are hard to explain, but were critical.
I’d put “person who makes sure WhatsApp verification codes work” on that list.
Thanks! That part of my job really wasn't too hard though, once I got things in order; but it was the easiest part of my job to describe. Just a lot of debugging from sparse data, and trying to get things to work a smidge better, because smidges here and there add up. It really helped to have a great customer service team that bubbled up usable information from users.
Debugging things from sparse data gets you involved in a lot of different systems though... That and I told people I worked at an ISP in the before times, so guess who got to fight with sendmail, and guess who got to own our Domain accounts and DNS accounts and guess who got to get x.509 certificates, and who had to fight with Google Apps to make mandatory 2fa usable, etc. Basically everything without a person and server adjacent got me. :P
Anyway, I've moved on (replaced by a team of three on the SMS stuff amyway, much better bus factor) and am semi-retired and no longer in any critical path, which is a lot less stress.