[exim] mysql + stats logging

I am toying with the idea of adding a router for all accepted messages to our system which will initally simply increment a counter in a mysql DB. ie to get hourly stats of all messages through system. we recieve 100k mails a day. Is this the prefered way to get real time stats, will it have much of a performance hit? Does anyone currently do this , or something siliar.

Both MTA and MySQL are on same switch so latency should be minimal...

Thanks
Ronan