Languages: Java/Kotlin OOD: SOLID/DRY/KISS principles, GoF patterns, MVC/MVP/MVVM/MVI architecture Jetpack: ViewModel, LiveData, LifeCycle, Room, Paging, Navigation, WorkManager, Compose Libraries: RxJava/RxAndroid, Dagger/Hilt, Retrofit/OkHttp, Gson/Moshi, Glide/Picasso/UIL/Coil, ButterKnife, Realm, Parceler, EventBus, GPUImage, Timber, JodaTime/ThreeTen, Dexter, GoogleMaps/OSM/YandexMapKit, Zxing, MPAndroidChart SDK: Firebase, Facebook/Twitter/OK/VK/LinkedIn, Google Play Services (auth, analytics, cloud messaging, drive, ads, location, activity, in-ap billing)