> You see a couple of ads mixed in your feed; behind that there's a big machine selling that space to advertisers and mixing it into the timeline of every user based on whatever profile Twitter has created for you. Then the advertisers want to know how their ads are doing, or they'll stop buying them…and you'll probably need to have salespeople to get them to put money into your ad system in the first place.

This is not crazily complex, bleeding-edge tech. This is something fairly well-understood and at any rate done by a lot of teams in a lot of places. (Twitter's ad profiling also seems awful. Maybe I am hard to pin down.) Probably the most complicated part is coming up with data to make advertisers think their campaign is working. (I am extremely skeptical most ad spend is actually worthwhile.)

> Twitter could be overstaffed. In fact it probably was overstaffed. But it's not overstaffed in the tune of of "it should be 10 people working out of a garage".

I agree 10 is too low for anything but bare-bones keep-the-lights-on-this-month maintenance, but it seems likely you could have a great and functional Twitter run by ~200 employees. I've seen more done with less.