If you are provided a Flowable that has no backpressure implementation (including ones derived from Observable), you can apply BackpressureStrategy using onBackpressureXXX() operators. These also provide a few additional configuration options. This can be helpful if, for example, you have a Flowable.interval() that emits faster than consumers can keep up. Flowable.interval() cannot be slowed down at the source because it is time-driven, but we can use an onBackpressureXXX() operator to proxy between it and the downstream. We will use Flowable.interval() for these examples, but this can apply to any Flowable that does not have backpressure implemented.
Sometimes, Flowable may simply be configured with BackpressureStrategy.MISSING so these onBackpressureXXX() operators can specify the strategy later.