Scaling just a bit

There's a lot of information (and hype) about scaling apps, distributing them on hundreds servers, putting them in the cloud using some existing PaaS or making your own (good luck with that). But what if you don't have a site with millions of visits that would justify those things and just want to make sure your app is (almost) always available with as little effort and smallest possible change to your architecture and application code. Do you have to apply the same principles when scaling from one to two servers as you would if the target number would be tens or hundreds of them. We had the chance of doing the the former and will discuss how we did it and experiences we had.