I don't run arsdigita.com any more, but I used to, and I also built the highest-volume web site ever done with the ACS, away.com, so even though I'm not yet privy to what went on today, I'll offer some comments.
The thing about sudden surges in traffic is that they expose little configuration issues and glitches. Arsdigita.com normally has pretty modest traffic in the scheme of things, and a site that doesn't get high traffic on a regular basis is unlikely to be optimally tuned and configured. When the traffic does arrive, it's all of a sudden a problem. Since the site seems to be running happily now, and it's the peak part of the day, I assume this is what happened, and that the problem has been corrected.
In any case, there's no rocket science going on here. Anything that uses an interpreted language and a relational database is going to have performance characteristics similar to AOLServer+tcl+ACS+Oracle. Get more things like application servers involved and the picture gets worse, not better. You could improve performance by writing in C++ and using a database without transactions, but this is courting disaster, and it's just not necessary. Given some tuning effort and adequate hardware our architecture scales just fine.
