Performance is not always important in every situation. Learning when performance does and doesn't matter is an important skill to acquire. A general rule of thumb is that if the user has to wait for something to happen, then it should perform well. If this is something that can be performed asynchronously, then the constraints are not as strict, unless an operation is so slow that it takes longer than the time window for it, for example, an overnight batch job on an old financial services mainframe.
A good example from a web application standpoint is rendering a user view versus sending an email. It is a common, yet naive, practice to accept a form submission and send an email (or worse, many emails) before returning ...
