[astrange]

Note WhatsApp had 35 employees when they were acquired and Instagram had 13. At that size you need to be productive at managing servers but you're probably not thinking how great it'd be to have a "whole new programming language and source control system" team.

[saagarjha]

WhatsApp and Instagram at the point of acquisition were simpler than Facebook is (and was), or even compared to what it is now. Once you scale you start to need a lot of engineers to help keep things standing up and everyone on the same page.

[Cederfjard]

WhatsApp had like half a billion monthly active users when they were acquired, that could be considered fairly large scale, no? But I agree with your point in general.

[TuringTest]

Yes, but WhatsApp is a point-to-point communication tool with mostly small groups. Each individual message doesn't need to be distributed to a potentially very large audience like in Facebook, making processing and coordination of nodes smaller and simpler.