[user5994461]

If you don't mind, I'd rather give a different view of WhatsApp and on-call.

It quickly turns out that WhatsApp could have a nice exit, so it made sense for some employees to sacrifice a bit of work-life balance, instead of looking for another job.

Your mileage may vary depending on "How many direct phone calls from customers does your company get when the service is unavailable for 10 minutes? and how much money is lost?" We don't have this data on WhatsApp.

[johnloeber]

Is there data on what the work-life balance at WhatsApp was like, pre-acquisition?

[user5994461]

Not that I know of.

Do you have experience in 50 people startup growing like mad and going worldwide? I've been there and I've seen how bad it can be for people responsible for the critical pieces of the tech. WhatsApp is no magic. Lots of hard work and elbow grease.