Someone here brought by some code that was throwing a MissingBackpressureException. Aaron and I narrowed it down to this snippet. `merge(range(0, 500).groupBy(i -> i % (RxRingBuffer.SIZE + 2)).observeOn(computation())).toBlocking().last()` it comes down observeOn requesting 128 Observables from groupBy and groupBy hard coded to request 1024 from range. We fixed his problem changing the `observeOn(computation())` to `flatMap(grp -> grp.subscribeOn(computation()))`2