It seems like a chapter may have been moved at some point during editing and references to this old order caused some confusion for me while reading. There are two references which tell me this.

At the end of chapter 5 (p125), which discusses the lifecycle of a request, it says:

Next, you will enter perhaps the most essential chapter of the whole book.
There are no performance issues to be solved if there is no visibility into them.
Let’s talk about monitoring.

The problem is that chapter 6 does not discuss monitoring and is titled:

Thinking Architecture for Performance

Then, at the start of chapter 8 (p191), it states (emphasis mine):

We are getting closer to the end of the book. So far, we have discussed all
kinds of topics and techniques related to the scalability of a Rails application:
database access, caching, software architecture, product design…we have
even discussed the structure of the Internet in the previous chapter.

Except chapter 7 is titled:

Designing Product for Performance

It seems like chapter 6 was originally chapter 7 or something similar and these two references were left in when one or the other was moved around.

Affected version: P1.0

Present in:

• Print copy from Bookshop.org
• epub file
• pdf file

Thanks!