In fact that would be the single most interesting point.
At least a ballpark of say around 20 machines with recent Xeons with ~ X gb ram to process say those 8k/sec.
P.S. In fact calculation were fairly lax and it should closer to 10k/s.
That heavily depends on which part of the stack you are looking at. (Event ingestion, processing, load balancers, databases etc.). There is a lot less hardware there than one would imagine ;)
It wouldn’t hurt to know about the databases if they are heavily used as part of processing
The data layer is probably more interesting from a scaling point of view in general since it's harder to scale, but it's also not exactly a point we're particularly happy with. There is already a comment from david (zeeg) on this post going into our plans there.
Finally I could understand what kind of efficiency you guys have. Not bad at all I’d say though not exactly “high load miracle” the article title would imply.