The right place to start planning for the required performance is in the design process. You should avoid belated code optimization, which could lead to unwanted side effects, bugs, or code that is harder to read and maintain.
Although the design gives you a more abstract impression of your application, you need to align it with constraints, such as hardware capacity or operational budgets, as well as the scaling characteristics you want and the expected amount of initial traffic.
Whether you are a cowboy coder or process geek, this section contains useful information because this chapter discusses designing PHP 5 applications in particular.
This is the first design rule ...