I tested it with 4k websites. The change made it only a couple of seconds faster
but requesting 4k websites would still take 4-8 seconds even if only 10 sites of
them are actually requested. For example before we did request each site 3 times
(12k times in total and triggered 12k events etc) which should be no longer the case.
The last `clearSiteCache` was there to free some memory but I think it shouldn't
be problematic to remove it. Also I removed one 'sort' as a lot of time is wasted
there. It should be in theory sorted afterwards anyway again. Need to see test
results whether this change is good or not.