Introduction: Performance, Media, and Real-Time

A mobile app shares limited CPU time, memory, storage, battery, and network capacity with the rest of the device. A design can work well on one phone and perform poorly on another.

This chapter explains how to choose the work the app performs, measure its cost, and reduce that cost without breaking the product's promises.

Start with the user action

“Make the app fast” is not a measurable requirement. Choose an action and define its result. Examples include opening a useful feed, displaying an image after scrolling, starting a video, or showing a recent driver location.