Tavish Armstrong wrote:It’s commonplace to say that computer hardware is now so fast that most developers don’t have to worry about performance. In fact, Douglas Crockford declined to write a chapter for this book for that reason:

"If I were to write a chapter, it would be about anti-performance: most effort spent in pursuit of performance is wasted. I don’t think that is what you are looking for."

Donald Knuth made the same point thirty years ago:

"We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil."

but between mobile devices with limited power and memory, and data analysis projects that need to process terabytes, a growing number of developers do need to make their code faster, their data structures smaller, and their response times shorter. However, while hundreds of textbooks explain the basics of operating systems, networks, computer graphics, and databases, few (if any) explain how to find and fix things in real applications that are simply too damn slow.

This collection of case studies is our attempt to fill that gap. Each chapter is written by real developers who have had to make an existing system faster or who had to design something to be fast in the first place. They cover many different kinds of software and performance goals; what they have in common is a detailed understanding of what actually happens when, and how the different parts of large applications fit together. Our hope is that this book will—like its predecessor The Architecture of Open Source Applications—help you become a better developer by letting you look over these experts’ shoulders.