The response is great.
For my WiFi/Xbee S6 accelerated updates 2min sampling update every 4minutes the ACK time over 700 POSTS time is between 200mS and 774mS. All POST succeeding 1st attempt.
For my Verizon/Xbee LTE at 15minutes sampling the ACK time is typically 5sec, very occasionaly about 1.5sec, and also 7Sec. For this test it delivered the outstanding readings that weren’t delivered previously, and then the new readings.
I am working on new feature Reliable Delivery, as cellular wireless range can vary and be unreliable. Often though there are periods of greater reliability (wind in the right direction). So if the first POST attempt doesn’t succeed, it is serialized to a QUExx.txt file to be retried when there is a connection.