Java 21 Virtual Threads + AI Workloads: What the Benchmarks Don't Show You (And What 16 Years Does)

I started writing Java professionally in October 2009 but had been working with C and Java since 2005 in college, on the side as well. I have watched every "this changes everything" moment in the JVM ecosystem — G1GC, lambdas, modularity, reactive streams. Each one was real, and each one had a trap the early adopters hit first. Java 21's Project Loom (virtual threads, GA) and its intersection with AI-augmented backend systems is the current one. Here is the practitioner's guide to what's real an