Hello,
thanks for inviting me:) I did several MySQL optimizations earlier, so this feels like a challenge. I bid $50, but it's rather symbolic, as I don't know what is the actual stage of your DB and the queries you're using. So I would need to see your DB table for tracking (enough if you can show CREATE TABLE dump), so that I will know about indexes, what engine you use, etc... Then I would need to see the SQL queries (in PHP) for insert/update/select. After that I can have better idea about the effort and time needed, so I can give better estimate.
If you invited me, I guess, I don't need to talk about past work, or introduce myself... But let me know if you would like to know more about me:)
Regards,
Luk
PS: Of course best would be access to DB, so I can also check the global settings, how much RAM you can use, and similar details...