RxKotlin is a specific implementation of reactive programming for Kotlin, which is influenced by functional programming. It favors function composition, avoidance of global state, and side effects. It relies on the observer pattern of producer/consumer, with a lot of operators that allow composing, scheduling, throttling, transforming, error handling, and lifecycle management.

Whereas Reactor-Kotlin is also based on functional programming, and it is widely accepted and backed by the Spring Framework.