In the evolving landscape of mobile applications, user expectations for performance and efficiency are high, necessitating a focus on app stability and optimization throughout the development process. Key performance metrics for Android apps include minimizing app launch time, which sets user expectations, and managing APK size by optimizing resources, using efficient image formats like SVG or WebP, and adopting Android App Bundles (AAB) for distribution. Network performance is also crucial, as slow load times can frustrate users, making practices like background data syncing, caching, and providing visual feedback essential for a smooth user experience. Additionally, efficient memory use is vital, requiring developers to avoid memory leaks and Out Of Memory (OOM) errors by managing object lifecycles and limiting data processing. The text previews further discussions on UI performance in subsequent parts of the series.