Let's say I don't have any trophies defined, and create my first one which awards a user for their first post ("user has posted at least 1 message"). When will existing users who have more than 1 post be awarded this trophy? Will it be awarded automatically or instantly upon creation of the trophy, without having to do anything, or will the award be triggered on their next post? If trophies are awarded automatically, are there any performance implications I should be wary of when creating trophies which may apply to hundreds of thousands of registered users (that's a lot of trophies to be handed out simultaneously!)? Is there any way to prevent these existing users from being flooded with alerts for new trophies?