Exponential Backoff using Rx.retryWhen()

ExponentialBackoff

// retries up to 3 times while exponentially backing off with each retry
                .retryWhen(errors ->
                        errors
                                .zipWith(
                                        Observable.range(1, MAX_RETRIES), (n, i) -> i
                                )
                                .flatMap(
                                        retryCount -> Observable.timer((long) Math.pow(4, retryCount), TimeUnit.SECONDS)
                                )
                )