Project Leyden is an ongoing initiative aimed at improving the startup and warmup times of the Java Virtual Machine (JVM). Building on the foundations laid by JEP 483, JEP 514, and JEP 515, the upcoming JDK 26 release will introduce JEP 516: Ahead-of-Time (AOT) Object Caching with Any GC. In this article, I explain the specific problems this feature addresses.

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JDK 26 introduces JEP 516, enabling AOT object caching with ZGC through a new GC-agnostic cache format. Unlike previous implementations that stored literal memory addresses, the new approach uses logical indices that are remapped at startup, allowing caches to work across different garbage collectors. The JVM automatically chooses between GC-specific (memory-mapped) and GC-agnostic (streamable) caches based on heap size and collector settings. Benchmarks with Spring Petclinic show approximately 26-28% faster startup times with minimal difference in cache size between the two formats.

Project Leyden & JDK 26: Bringing AOT Caching to ZGC