WhatsApp used to be hosted on ~15 bare metal servers serving 100 million concurrent users...

They were also acquired at a price which would value each employee at ~350M.

They were capable of scaling in a way that is certainly an anomaly, and not indicative of the costs of an ordinary team.

It speaks volumes about what the right talent and architecture/technology choices can do if leveraged successfully, but is more of an interesting anecdote than a realistic infrastructure budget.

> They were also acquired at a price which would value each employee at ~350M.

That’s a pointless calculation. The acquisition wasn’t for the employees. As with all network-effects products, the acquisition was for the active user base. They could have acquired WhatsApp, fired the engineering team, rewrote it with an architecture that required 100x the servers and still been happy.

It speaks volumes about Erlang/BEAM I think

I find this so fascinating, is there more info on the software/hardware during this time period?

Before ist was possible to Share Images. BTW they used s3 dir that

We have give or take 30M monthly active users.

The instances we use are not the largest (we use 2xls) but we also incorporate spot instances as part of our autoscaling.