Spring Cloud provides tools for building distributed microservices. I use Spring Cloud Netflix Eureka for service discovery—services register themselves and discover others dynamically. Ribbon enables client-side load balancing. Feign creates declarat

JUnit 5 provides a modern testing framework with @Test, @BeforeEach, @AfterEach lifecycle hooks. Mockito creates test doubles with @Mock and @InjectMocks annotations. I use when().thenReturn() to stub method responses and verify() to confirm interacti

CompletableFuture enables non-blocking asynchronous programming in Java. I use supplyAsync() to run tasks in thread pools and thenApply() to chain transformations. thenCompose() flattens nested futures, while thenCombine() merges independent futures.

Global exception handling in Spring uses @ControllerAdvice to centralize error responses across all controllers. I define @ExceptionHandler methods for specific exceptions, returning consistent error DTOs with HTTP status codes. Custom exceptions exte

Spring Data JPA eliminates boilerplate DAO code with repository interfaces. I extend JpaRepository to get CRUD methods automatically—save, findById, findAll, delete. Custom query methods use method naming conventions—findByEmailAndActiveTrue generates

Java Streams provide a functional approach to processing collections with operations like filter, map, and reduce. I use stream() to create streams from collections and apply intermediate operations that are lazy and return new streams. Terminal opera

Spring Boot simplifies building production-ready REST APIs with minimal configuration. I use @RestController to create RESTful endpoints and @RequestMapping to define routes. The @GetMapping, @PostMapping, @PutMapping, and @DeleteMapping annotations h

Android performance optimization ensures smooth 60fps UI and efficient resource usage. I use Android Profiler to monitor CPU, memory, network, and energy. Layout Inspector identifies overdraw and deep view hierarchies. Systrace captures system-level t

ProGuard and R8 shrink, obfuscate, and optimize Android apps for release builds. R8 is the default tool, combining shrinking and desugaring. I configure rules in proguard-rules.pro—keeping classes used by reflection, serialization, or native code. -ke

Deep links open specific app content from external sources. I configure intent filters in AndroidManifest with URL schemes—http, https, or custom. App Links verify ownership via assetlinks.json on your domain, providing seamless no-dialog opening. Int

Google Play Billing enables selling digital content and subscriptions. I integrate the Play Billing Library and initialize BillingClient with PurchasesUpdatedListener. Query available products with queryProductDetailsAsync(). Launch purchase flow with

Services run background operations without UI. I extend Service and override onStartCommand() for started services or onBind() for bound services. Foreground services use startForeground() with ongoing notification, required for long-running tasks vis