Maybe it needs up to 5 seconds to warm up if it's in deep sleep, so splitting this into three 2s periods provides the least frustrating user experience.
As soon as you need to deal with real hardware things always start to get complicated.
https://www.sharetechnote.com/html/Handbook_UMTS_RrcStateCha...
- press button
- gprs roundtrip about button press with "no payment, free ticket" (2s)
- machine shows "printing ticket", asks server what to print (aka the idiotic unnecessary step)
- gprs roundtrip (2s)
- printer warmup? (?s)
- prints ticket
> to save power (and possibly SIM cost)
Nope, costs per sim are monthly per card, until you hit the data limit, then per MB. Those machines typically have enough power to keep connection alive.
It's not a new scenario. It happened to me.
I'm not mildly inconvenienced by some honking. That's just aggravating. I'm inconvenienced by having to call to get a receipt.
In my country, we have a similar system, and before my bank sends me a push notification about the outgoing transfer, the push notification for incoming transfer pops up for most of the time. The delay between push notifications rarely goes above 2 seconds.
Ours has an upper limit to prevent abuse of the system, but you can't beat instant, actually.
After I had to add a special animation for one email system so that user was sure that "the core functionality of encrypting" was indeed working (it took milliseconds in reality), your experience doesn't surprise me that much. But, in my "IoT" system we have a mix of devices. Our service can handle most requests in sub millisecond, but some devices (gprs) need at least minimum 1 second (20sec is still within time limit) to respond only because of slow connectivity. And then I have a parking ticket machines where you press button, wait 2 seconds, it beeps, then after 2sec it changes screen to "printing ticket", then after 2s you get the ticket, where everything can be a local action (free ticket without payment). Technology is wild.