Virtual threads for concurrent throughput

Platform threads incur nontrivial costs, requiring thousands of CPU instructions to start and consuming megabytes of memory, making separate platform threads infeasible for high-concurrency server applications. Instead of non-blocking APIs with deeply nested callbacks, use virtual threads to make blocking cheap. Since Java 21, virtual threads allow familiar structures like branches and loops during I/O waits, as the underlying platform thread unmounts the blocking virtual thread to run others. Utilize Executors.newVirtualThreadPerTaskExecutor() to create an ExecutorService handling large numbers of concurrent, I/O-blocking tasks. Avoid virtual threads for CPU-intensive work; use parallel streams or recursive fork-join tasks instead. Note that while JEP 425 introduced them in Java 19, they transitioned through preview in Java 20 before finalization. Scope: Java. Reviewed October 4, 2026.