I think that might be common enough these days through sound horizontal scaling principals and especially services that scale for you, but Whatsapp launched in 2009, pretty much the turning point for the tech that enables "web scale".

At that time AWS was just rolling out ELB and RDS, people were still fulfilling their (and most) roles on EC2 servers or even more likely dedicated servers / VPS that took day(s) to commission and might have even been setup by hand, there was no Docker, GitHub was new and Actions, Jenkins etc were years away, and there were very few PaaS- or IaaS-type offerings IIRC just a very nascent Heroku and Google App Engine.