Spring Boot 4.0 has been launched, bringing enhancements such as cleaner modularization, improved observability with Micrometer, and the adoption of JSpecify for null-safety, all of which improve memory usage and streamline development processes. This release marks a significant collaboration between JetBrains and the Spring Framework team, with Kotlin 2.2 now established as the official baseline version, allowing for a more integrated development environment. The Kotlin compiler and IntelliJ IDEA support JSpecify annotations natively, enhancing null-safety checks between Kotlin and Java. API versioning and bean registration in Kotlin are streamlined and concise, reflecting Kotlin's expressive nature. These developments are expected to encourage broader Kotlin adoption among backend developers seeking to leverage modern language features, with JetBrains continuing to ensure robust integration within the Spring ecosystem.