http://blog.phpfog.com/2011/03/16/scaling-php-up-out-and-around/ http://blog.phpfog.com/2011/03/16/scaling-php-up-out-and-aro... I want to share this article (

http://blog.phpfog.com/2011/03/16/scaling-php-up-out-and-around/ http://blog.phpfog.com/2011/03/16/scaling-php-up-out-and-aro... I want to share this article (which I wrote at PHP Fog) about scalability (in PHP but applies to all web apps) and the scenario you are asking about. I agree with travisglines (and everyone else on the thread), that this scenario you are talking about is in fact rare. It's one of those good problems to have. ("I have so much money, how am I going to spend it all") Most people who I talk to care about scalability, not because they need it now, but rather because they want it as insurance. It sounds like you are in the same boat. My recommendation is to pick a hosting platform that allows you to build your application the same way you normally would, but allows scalability if you do need it. Heroku already does this for you for RoR; Windows Azure does this for .NET apps; GAE for Java/Python; and PHP Fog for PHP. Those platforms basically make caching and scalability really easy. Other than scalability and caching, you should build your application with performance in mind; as having a fast site is important regardless of the number of users. mryan & mooism2 referenced some good resources for doing exactly that.