RxJava utilizes a concept of reactive streams by introducing Observables, to which one or many Observers can subscribe to. 

Dealing with possibly infinite streams is very challenging, as we need to face a problem of a backpressure.

It's not difficult to get into a situation in which an Observable is emitting items more rapidly than a subscriber can consume them. 

We will look at the different solutions to the problem of growing buffer of unconsumed items.

https://www.baeldung.com/rxjava-backpressure