How could they all go down at the same time, if they have different teams of engineers running each product separately?
Could anyone with some background (or person familiar with the matter) explain how their system's set up?
edit: though saying that, they do run their own registrar... Might've fucked something up over there.
FWIW, WhatsApp (on phones) should be resiliant to a DNS only outage, the clients contain fallback IPs to use when DNS doesn't work, and internal services don't use DNS as far as I remember.
At one time, WhatsApp had actually separate infrastructure at SoftLayer (IBM Cloud now), but that hasn't been in place for quite some time now. When I left, it was mostly just HAProxy to catch older clients with SoftLayer IPs as their DNS fallback.