We wrote our bidder (in app advertising) in Go. It is globally distributed (close to the exchanges) and handles 1.5-2M requests/s (OpenRTB,~50-90k/s per instance) with a p99 of 10-20ms (without network latency). Really happy with Go, especially the GC improvements done by the Go team in the last few releases. For a previous similar project we used Ruby which was quite a bit slower.