AbuseFilter seems to be running quite expensive (relatively) autopromotion code for every request, that involves RPC:
4.3 > AbuseFilterHooks::onGetAutoPromoteGroups 57.4 > memcached::get
0.000427 3.5 < memcached::get
0.000714 0.0 < AbuseFilterHooks::onGetAutoPromoteGroups
I suggest doing it only when 'expensive' checks are done (e.g. preview, save and editform).