What reactive programming libraries have you worked with?

In Java, for reactive programming, I often use the libraries Project Reactor and RxJava.

• Project Reactor is the foundation of the reactive stack in Spring WebFlux, providing Flux and Mono for working with data streams.
• RxJava is a popular library with a rich set of operators for reactive programming, often used outside of Spring.

Example of using Reactor:

Flux.just(1, 2, 3)
    .map(i -> i * 2)
    .subscribe(System.out::println);

I am also familiar with using reactive drivers for databases, such as R2DBC for Postgres, which allows working with databases in a reactive style without blocking.