"From SMTP filters/routers that handle millions of email deliveries a week to in-memory message journaling (for redundancy) that handle hundreds of transactions per second."

I stopped right there. To me, high performance is for instance, handling millions of emails per minute, thousands or tenth of thousand TPS. This is high performance, real life performance, not seen only in "physic labs and university research centers".

Some comments talk about Tcl using select. If this is true, it would mean a max of 1024 connections in parallel, kind of sad...