Hi!
15 to 20 sec to refresh values? What API are you using that lasts so long?
In my demo IIoT APP where my laptop works as server and replies external calls (and I have a poor upload speed too), the updating lasts 8-10 sec but if I had used a Webhook, the process would last 4-6 sec.
Of course, while more data is requested, the updating will last more (my demo uses 12 variables)
Saludos Joshi.