When you move beyond using one instance for your database, what is the best practice when using EC2? If the first instance is a master and you're spinning up slaves, they would need to scan the transaction log and bring themselves up to date before the slaves are useable correct? If the master had been running awhile and was busy, this could take a very long time, right? Is it smarter to use something besides master-slave on EC2? I've seen MySQL Enterprise has support for EC2 but it wasn't clear (to me) on the MySQL site what features this adds. Does it have some added functionality that makes spawning new instances fast and turnkey-like?
Fundamentally, I'm trying to figure how you auto-scale the database.