Having written some analytics services myself, I'm curious what sort of performance you're seeing on the ingest side with tornado/python. What kind of throughput per server (or systemwide) are you seeing?
The ingest side isn't too crazy. We're doing between 50-100 insert-type requests per second per server (although we run multiple instances of Tornado per server so it's actually fewer per Tornado process). The stats on the read side are more impressive. :)