we have been able to scale memcached to handle 200k UDP requests/s with an avg latency of 173us. This is from 50k UDP requests/s using the stock version of Linux and memcached.
Tag: memcached
memcached Usage
alibaba and yahoo are using memcached
New memcached release
1.2.0 brings reduced CPU usage and increased memory efficiency, plus bug fixes
Gregor J. Rothfuss 