[HowardRoark]

There are different levels of scaling, and for different kinds of apps, the trade offs that you can make are different. Unless you are making a really huge leap, most of the time it will be a gradual process. So unless you are talking Google or Twitter Scale in a matter of months, it may not be as bad as it sounds.

Monitor, optimize your current configurations, cache, load balance, cluster, use messaging, use existing industry knowledge on distributed systems, read academic papers and innovate... For advanced distributed systems, checkout Prof. Indranil Gupta's lectures amont many others: http://www.cs.uiuc.edu/class/fa10/cs425/lectures.html