According to the Cambridge dictionary, one of the acceptations of performance is "How well a person, machine, etc. does a piece of work or an activity." If we put it together with "high" we can define it as the output or efficiency with which a task is being done.

High performance in software refers to the strategies that developers adopt to create pieces of software that can perform a process efficiently. When we are developing mobile software, this affects, but is not limited to, layout development, energy and battery management, security concerns, efficient multithreading, programming patterns, and debugging techniques.

There is a big difference between doing things, and doing things right. In a real world with deadlines, budgets, and managers, software engineers fall very often into acquiring technical debt. A technical debt is "bought " (if we can use that verb) when a system is developed without a complete or proper design, moving problems forward instead of correctly addressing them. This has a snowball effect: at an advanced stage, the technical debt is so high that further development is very costly, and this leads to a dead point or astronomical damage to budgets in organizations.

While deadlines cannot always be avoided, adopting an efficient development process in any software development is vital to delivering good quality at a reasonable cost. It also means that the development skills become more mature in a developer, and instead of achieving tasks that fulfill the requirements, engineers can develop software that is efficient, robust, and that can be further extended in the future (what we called "maintainability").

This book introduces techniques for constructing high-performance software for Android devices.