We implement windows update through proxy without delay pool and there's no problem at all.
acl fast dstdom_regex download.windowsupdate.com update.microsoft.com acl fast dstdom_regex download.microsoft.com ds.microsoft.com #direct bandwitdhfull access to websites delay_class 1 2 delay_parameters 1 -1/-1 -1/-1 delay_access 1 allow fast delay_access 1 deny all
