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Spring's event mechanism enables loose coupling between components. ApplicationEventPublisher publishes events. @EventListener handles events asynchronously or synchronously. Events extend ApplicationEvent or are POJOs. @TransactionalEventListener pub

Project Lombok generates common Java code via annotations at compile-time. @Data creates getters, setters, toString, equals, and hashCode. @Builder implements the builder pattern. @Slf4j provides logger instances. @NoArgsConstructor and @AllArgsConstr

Multi-tenancy serves multiple customers (tenants) from single application instance. Schema-per-tenant isolates data in separate databases. Shared schema with tenant ID column partitions data within tables. Discriminator-based approach uses JPA filters

Kubernetes orchestrates containerized applications at scale. Deployments manage ReplicaSets ensuring desired pod count. Services expose pods with stable endpoints. ConfigMaps externalize configuration. Secrets store sensitive data. Resource limits pre

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

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

Spring WebFlux enables reactive, non-blocking applications using Project Reactor. Mono represents 0-1 elements, Flux represents 0-N elements. Reactive programming handles high concurrency with fewer threads. I use reactive repositories with R2DBC for

SLF4J provides a logging facade, Logback implements it efficiently. I use logger levels—TRACE, DEBUG, INFO, WARN, ERROR—to control verbosity. Parameterized logging with {} placeholders improves performance versus string concatenation. MDC (Mapped Diag

Spring Cache abstraction simplifies caching with annotations. @Cacheable caches method results—subsequent calls with same arguments return cached values. @CachePut always executes methods and updates cache. @CacheEvict removes entries or clears entire

Spring Security secures applications with authentication and authorization. I configure security with SecurityFilterChain bean defining protected and public endpoints. JWT (JSON Web Tokens) provides stateless authentication—tokens contain user claims

API versioning manages evolution while supporting existing clients. URI versioning uses paths—/api/v1/users, /api/v2/users. Header versioning employs custom headers—X-API-Version: 2. Content negotiation uses Accept headers—application/vnd.myapi.v2+jso

AOP separates cross-cutting concerns from business logic. Aspects modularize logging, security, transactions, caching. @Aspect defines aspect classes. @Before, @After, @Around specify advice timing. Pointcuts select join points using expressions. @Aro