Why GC Still Matters in 2024 Even with better APIs and faster hardware, garbage collection pauses remain one of the top causes of latency spikes in Java services. A 200ms GC pause in a payment processing service is a customer-visible failure. A 50ms pause in a trading system is a missed execution window. Java 21 delivers Generational ZGC — the most capable GC Java has ever shipped — as a production-ready, non-preview feature.