•Core Java (OOP, Streams, Concurrency, JVM, Garbage Collection)
•Spring Boot & Spring Framework (IoC, AOP, Actuators, Profiles)
•Microservices Patterns (Saga, Circuit Breaker, Service Discovery, CQRS)
•Database & Caching (PostgreSQL, MySQL, MongoDB, Redis)
•Distributed Systems & Messaging (Apache Kafka, RabbitMQ, DLQs)
•Containers & DevOps (Docker, Kubernetes, CI/CD Pipelines)
•Real-world System Design FAQs (UPI, Aadhaar, Rate Limiter, TinyURL)