Interview questions for Java engineers with five to eight years of experience: advanced Core Java and JVM behaviour, Java design patterns, advanced Spring Boot, Spring Security in depth, microservices at scale, and microservice design patterns. Starts with a rapid revision of the earlier tiers.
Rapid revision of every 2–5 year question, with one-line answers and links to the full answers.
Design scenarios, immutability and singletons, concurrency and atomicity, JVM memory and references, class loading, reflection, annotations, records and sealed classes.
Creational, structural and behavioural patterns — how they work, how to implement them in Java, trade-offs and when to avoid them.
Logging and configuration precedence, transactions and multiple data sources, validation, REST design, reactive and async processing, deployment, HA and custom starters.
Securing REST APIs end to end: JWT contents, stateless auth, banking-grade practices, service-to-service security, method vs URL security and core classes.
Migration from monoliths, Spring Cloud, data consistency and sagas, Kafka integration, tracing, discovery, load balancing, service mesh, scaling and security.
API gateway, circuit breaker, retry, service discovery, database per service, saga, choreography vs orchestration, bulkhead and strangler fig.
