>At a relatively early stage startup many of the techniques are overkill, or simply out of reach, but it's nice to peer around the corner and get an overview of the approaches and problems of performance at the next order of magnitude of scale.
I wouldn't say that they're necessarily overkill or out of reach, but things to keep in mind as you're designing and building your software. Making sure that you can measure and instrument your code can save a lot of grief later on, even if it doesn't make sense to be doing those measurements right now. The flowchart is absolutely true: You can't prove that it's fast without measuring it.
The first few chapters in particular are a nice introduction to reasoning about performance, and the availability in multiple formats is also nice!