Slow aggregate performance

Hello,

Is there any way to improve the performance of Aggregate server, that has become really slow during login -> redirection.

Also, the _security_revisions table in aggregate, there are over 4 Million entries in this, if this is used for "_security_revisions -- used for inter-process signalling of permissions changes" can we remove all data from this table? i.e. if these are only logs.

Thanks!