Update:
I have confirmed 100% the source of the these spikes were very aggressive, rogue, unidentified bots originating on Chinese networks. After blocking the resident networks of these bots, all spikes have stopped, completely.
This is a "huge success story", going from unknown, uncorrelated performance hits / spikes due to nearly random spikes in performance to cause identification and total resolution. As you can see from the graph over the last 24 hours, there have been zero spikes.
I will keep the same MQTT and Node-RED instrumentation in place (which I am very pleased with) and will also keep all "spike trapping" instrumentation and DB logging in place, so if other spikes appear, which I am fairly confident more of these "pesky" bots will appear sooner or later, I will trap them, identify the source and block their resident networks.
Success!
MQTT and Node-RED did not "solve the problem". MQTT and Node-RED provided a very powerful and flexible way for me to quickly instrument custom sensors and logging, which helped me identify the problem.
I highly, recommend MQTT and Node-RED. These tools are free. Thank you very much MQTT and Node-RED developers!