What configurations need to be set for a LAMP server for heavy traffic?

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http://serverfault.com – I was contracted to make a groupon-clone website for my client. It was done in PHP with MYSQL and I plan to host it on an Amazon EC2 server. My client warned me that he will be email blasting to about 10k customers so my site needs to be able to handle that surge of clicks from those emails. I have two questions: 1) Which Amazon server instance should I choose? Right now I am on a Small instance, I wonder if I should upgrade it to a Large instance for the week of the email blast? 2) What are the configurations that need to be set for a LAMP server. For example, does Amazon server, Apache, PH (HowTos)