+ /**
+ * A wild estimate on how deep a queue should be. Without having knowledge of the remote actor we can only
+ * guess its processing capabilities while we are doing initial buffering. With {@link AveragingProgressTracker}
+ * this boils down to a burst of up to 2000 messages before we start throttling.
+ */
+ private static final int TARGET_QUEUE_DEPTH = 4000;
+