>if i recall from early Zynga (circa 2008), we would get MySQL (InnoDB) on decent commodity hardware (Dell 2U with 8 cores, 32G mem, 15K RPM disks in raid 10, cost about $7K USD) to around 6K QPS before it would eat shit.

Mysql is slow for concurrent access, but not that slow. I don't have mysql installed, but postgresql running on openbsd (a famously poorly performing OS) in a virtualbox virtual machine (hooray overhead) only being given one core and running off of a slow laptop hardrive is beating that for me.