In many of the interviews from the so called gurus there is a sentence that repeats pretty commonly “you can forget about scaling, because the platform will handle that”, in my opinion it’s only “partially true”.

When you host your application in your own set of servers you can detect performance problems, since your number of servers is fixed and the response times vary, so you can identify and fix that problems.

The problem with the clouds can arise not when the users are browsing your site, but when your cloud provider sends you the bill :).

One of the parameters they take into account (obviously) is the CPU cycles your application uses (Google, Amazon, Azure), so the “infinitely scalable infrastructure” can hide your performance problems and cost you a good amount of money :)

So the optimization in “cloud based” websites should be as important as in “traditional” applications.

Another problem can be the creation of artificial traffic (and cost) by botnets, competence, crackers and so, it can be similar as when someone bombs your adsense ads and gets you out of the program.

So unless your money can scale infinitely,  it’s not always a good idea that your app scale infinitely :).