WHAT THE BOOK TEACHES
It's easy to think of performance as one thing: how fast an app can process a request. But in truth, performance is a complex combination of software, hardware, your user's device, app design and psychology.
Every app works on two layers: one layer is hidden and one is visible: one is complex to the point where a human brain cannot even begin to process it - the other working solely and intentionally to hide that fact. Your job as a developer is to break the chain between the two layers and make complicated stuff seem easy
User-perceived performance is the only performance that matters. In the stage show that is your app, you are the magician. You get to tell the user what to do and where to direct his attention. You get to prepare the stage, the machinery, the tools and equipment and train the beautiful assistant to do exactly what you want to avoid breaking the illusion. The user doesn’t need to know what’s going on backstage.
If you do your job right, they’ll believe it’s magic. If you reveal your trick, or complain how hard it is to do, you’re not helping your audience - you’re ruining their evening.
