> And what I’m getting to is that yes, they had 50 engineers in their pay roll, but many more supporting various SaaS products and infrastructure they use and pay for.

I was at WhatsApp from 2011 to 2019.

Hardware was outsourced to SoftLayer, of course. I think they had a sizable operation, but if you move that in house, you've got a team of 4ish for 24x7 colo work (we were only in one location for an embarassing amount of time), plus a networking person, and maybe a manager. We certainly got better service with SoftLayer's larger team including ease of getting more servers, but we would have had better visibility in house, so it's a tradeoff. Softlayer's staff was probably smaller than the combined staff if all of their major customers in-sourced, anyway.

Other than that, we used multiple providers for SMS and voice verification; some of whom have a lot of staff. You need more staff for this, IMHO, because in addition to 24x7 coverage, you also need to arrange connectivity with carriers in all timezones and all languages. But some of the companies we used seemed pretty small, so I dunno.

We were using Zendesk in our customer service system after growing out of Gmail and before in-sourcing it after aquisition, and Dyn for DNS (which doesn't take much staff to insource).

What other SaaS do you think we used? Do you want to count the OS app stores and push services? Maybe payments while that lasted? G Suite for corporate email when forwarding to personal mail became too silly?

We self-hosted our code repository and bug tracker.

I hope I didn't come across as though I was criticizing at all. I meant to point out that having 50 engineers build something today means something different than it would have a decade ago, although in retrospect my age/career are getting away from me and 15-20 years ago would have been a much better example.

I should emphasize that the accomplishment is incredible, regardless of how much we outsource things today. I know you didn't outsource crucial talent or the ability to deliver a good core product; you can't do that as far as I know.

I apologize if it seemed like I was putting down the accomplishment. I'm only meaning to reflect on how much more technical and infrastructure work happens outside of our teams these days than it has in the past. Perhaps though it isn't how much _more_ happens, but how _different_ what happens is. Building these products has changed a lot in some ways.

Edit: Also thanks for overview, that was a cool cursory look at how you operated.

No offense was taken.

I mean, honestly the way we built WhatsApp 10 years ago is pretty similar to how we would have built it 20 years ago... except that we'd probably have had to move towards dedicated colo space, instead of 'managed hosting' bare metal. I think we may have ended up going that way if we didn't get acquired and move into FB datacenters.

SMS aggregators were certainly around in 2000, just as well as in 2010 and 2020 ... although they've got fancier webpages now.

I mean, you can outsource a bunch of stuff, but we just didn't use very much. You can't outsource the core product and deliver reliability, and we didn't have much that isn't the core product. SMS verification was only reliable (ish) because we used several providers with real time statistics guiding the choice. (Of course, some of the providers use the other providers, so it's very messy)

Whatsapp used bare metal servers. It isn't hard to do, just that people no longer learn to do it.

> Ten years or longer ago I suspect the story would be different

Whatsapp was built 12 years ago.

I assumed they did their largest scale ups more recently, though. I could be wrong!