Coroutines: Waiting Without Freezing

The main thread

Everything your user sees runs on one lane of execution called the main thread. It redraws the screen dozens of times a second, and it handles every tap, scroll, and animation. It's fast — as long as nobody makes it wait.

A network request to the PawWalk backend takes anywhere from 50 milliseconds to several seconds on hotel Wi-Fi. If the main thread stood still waiting for that response, the app would freeze: scrolling dies mid-flick, buttons ignore taps, spinners stop spinning. Users experience it as "the app is broken" — and Android will eventually show an Application Not Responding dialog and offer to kill it.

So the rule is: the main thread may start slow work, but it must never stand around waiting for it.