If performance is a design goal, you need to take it into account. Making things efficient can affect the code in funny ways and/or introduce restrictions you n

If performance is a design goal, you need to take it into account. Making things efficient can affect the code in funny ways and/or introduce restrictions you need to plan around, so ideally you need to be thinking about it as early as possible. You can't get everything right in advance, but making an educated guess is better than just ignoring the issue and then wondering later why it's proving so difficult to improve the performance. People already think in these terms, I am sure, when it comes to loading data over the internet, or reading larger-than-RAM data sets, and so on.