> Because we use eventlet, we need a pure python memcache client so that eventlet can patch the socket operations to be non-blocking.

Not true. ultramemcache (https://github.com/esnme/ultramemcache) is an example of a c++ memcached client that is friendly to gevent's monkeypatching. It does this by importing the socket library via the python runtime (https://github.com/esnme/ultramemcache/blob/master/python/um...), rather than using a native construct.

My experience is with gevent, but I suspect that eventlet's monkeypatching is similar to gevent.