Spring Boot: Dependency Injection, REST APIs, Spring Security (JWT), JPA/Hibernate, Transaction Management, Actuator, Configuration Management, Spring boot Input Validation (Controller Layer), Global Exception handling (Controller Advice Classes), Spring Boot Annotations, Rest Template, WebClient. Microservices Architecture: Service Decomposition, API Design, Resiliency Patterns, Circuit Breaker, Distributed Transactions, Scalability, Observability Components, Services, RxJS, State Management, Routing, API Integration, UI Performance Optimization.