BG threshold & Insulin Secretion?

Hi there, I am trying to understand at what BG levels, your pancreas will release insulin to cover the high blood glucose. I understand there is continuous release of basal insulin but bolus insulin releases when a certain threshold of BG reaches. Do you have any studies to point out to or your personal experiences based on your BG monitoring, particularly if you are wearing a CGM. I was doing some trials and it seems to me even for a small amount of carb, my sugar will still go up to 7 before it starts lowering. This makes me think that my bolus starts releasing only at that threshold? I am talking of plain carbs (no high GI or fats included that could hamper BG rise and thus insulin secretion).

I have no insulin resistance, so any insulin released should be used right away.

Any thoughts? thank you in advance.