There is always the desire to have a one size fits all solution. Even more so, the startup project of smaller companies want to be able to grow without change. They want to be able to start in one direction without having to transfer from one method of business to the next. When this is possible and pragmatic, it should be done.
When is it pragmatic to consider implementation more vital than a never changing concept of doing business? Considering the topic of this book is web technology, we might realize it will happen more often here than any area of business. In fact, we might look silly promising no change to a business-minded person.
So another approach would be to minimize and facilitate change. Refactoring is far better than rebuilding when possible. This can be approached with stable libraries and with existing tools. There are other times where the personality of the business may drive creative new solutions. When we move into those areas, there are libraries out there like jQuery that allow custom solutions to be built around stable, flexible solutions.
Now with all that said there are several ways to scale. One is to just optimize the slow pages, files, and data interaction. Caching is another method of scaling that is becoming more popular. Just remember scaling is one goal that should not cause neglect of other issues to achieve it.