Scaling a product like that is an incredible engineering achievement, but I am speaking specifically about product development. What other products has Facebook innovated internally, worked through the product-market fit, and scaled itself? Again, my point is that they have a ton of resources and a huge existing user base, but the only successes they seem to have are purchasing companies that are ramping. They deploy engineers and connect to the existing user base, but they aren't innovative in product design.

8x scaling over a time period where the available size and performance of single-image systems increased by more than 8x seems… if not trivial, at least not an “insane achievement.”

“Scaling” as in “making sure the infrastructure can handle much higher load”, or as in “making sure the product remains genuinely useful to people, so that the user numbers go up and not down”? For both, it didn’t happen by itself, but it’s far from rocket science. A sane team of 15-20 people can do it.

Was it just because WhatsApp was already generally well designed when they purchased it?