Nice, in this case, should be nice implement a cache server, and mysql servers will send cache to it? something like:

50000 mysql clients (no cache here) < - >10 mysql servers (100mb of cache each) < - >2 cache servers (16gb of cache each)

we could use local cache + remote cache, for example, with this the local cache will be very fast, and the remote cache will have a network delay (but it's faster than disk i/o)

what you think?