Java 21 to 25: 22.7% increase in throughput (RPS) and a 20.1% reduction in average latency.

A real-world benchmarking report from Trendyol's International Payment team comparing Java 21 and Java 25 (LTS) performance. Upgrading to Java 25 delivered a 22.7% increase in throughput (RPS) and a 20.1% reduction in average latency, along with 63–120MB lower RAM usage and 50% less network data overhead. Key migration notes include enabling -XX:+UseCompactObjectHeaders (not on by default), upgrading Gradle to v9.1+ for Java 25 compatibility, and rebuilding rather than just swapping the runtime image to fully benefit from optimized class/data layout. Post-production rollout showed ~10% memory reduction.