This isn't mission critical data. There's no reason to worry about the possibility of a minuscule number of clicks not being counted. I've done this with a 250k+ tgp with well over a mil clicks and didn't notice many issues.
This was just logging clicks to thumbnails so they could be ordered by productivity so data was collected every 5 minutes and batch inserted into mysql. The numbers in my own click count and what the trade script counted were extremely close.
If I were that worried about not missing a single click ever then memcached would certainly be an option.
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