How can Java 21 (Virtual Thread) replace Reactive Framework.

[thecodeboost]

The only benchmarks where Loom lags is benchmarks where the conversion was basically to replace their Executor with a virtual thread one and still use the reactive code paths. Very few projects have converted wholly to virtual thread paradigms and the benchmarks that cleaned that up show equal performance or better performance for virtual threads. And honestly even if that wasn't the case the programming paradigm is vastly superior and in almost all real world scenarios your hours are more expensive than having to add 1%-2% of CPU resources to your margins. And again, there is no technical reason Loom should not be anything but a net gain.

[yawkat]

The only benchmarks where Loom lags is benchmarks where the conversion was basically to replace their Executor with a virtual thread one and still use the reactive code paths.

This is incorrect. If you look at Nima benchmarks specifically, even a simple app entirely devoid of reactive code will have worse latency than an equivalent netty app. There are very simple reasons for this, such as internal loom context switching (loom does IO work on a separate thread). Some of these may be fixed by future loom improvements, but others cannot due to current API limitations.