Use when writing, reviewing, or upgrading a Java service on JDK 21 LTS or newer; designing records, sealed interfaces, pattern matching, virtual threads (Project Loom), and structured concurrency; building Spring Boot 3 services (Spring Web, Spring Data JPA, Spring Security, Actuator) or evaluating Quarkus, Micronaut, Helidon for native image; tuning the JVM (G1, ZGC, heap sizing), reading JFR recordings, running async-profiler; managing Maven or Gradle builds; testing with JUnit 5, AssertJ, Mockito, and Testcontainers against real Postgres or Kafka.
