JDK 19 is released with Loom https://jdk.java.net/19/
And they may plan to remove Continuation in future, so it should be better to use Virutal Thread directly?

Some of synchronized usages need to be replaced with Lock eg: pgjdbc/pgjdbc#1951

Yes. The microbenchmark guards a very short-lived in-memory operation, and so irrelevant for the places where ReentrantLock is actually helpful for virtual threads. Virtual threads work well with either ReentrantLock or synchronized in these cases. It's only the cases where synchronized guards a long-running and frequent operation that might adversely affect virtual threads' scalability. --- @pron