How fast is telepathic communication (with a familiar)?

The spell description of the spell find familiar states:

While your familiar is within 100 feet of you, you can communicate with it telepathically.

Which to me raises a question: how fast is this communication?

Speed is often defined in latency – delay until the first bit of information arrives – and throughput – amount of information per second.

I believe I can be quite sure that the latency will be no less than that of regular speech which at 100 feet is next to nothing1

But when it comes to the throughput I seem to be in the dark – how quicly can concepts be explained through telepathic comunication?

This becomes important especially in the case of familiars when looking at surprise rules.

A member of a group can be surprised even if the other members aren’t.

So, the familiar’s awareness doesn’t directly benefit the wizard unless it is able to timely communicate the presence of foes to the wizard.

How quickly can a familiar warn its wizard of the oncomming danger? Is that instantaneous, is it as fast as regular speech, or something in between?

1 100 feet divided by 1124 feet/s = 0.08 seconds with the speed of sound. Telepathy doesn’t require air so probably goes with the speed of light resulting in 0.0000001 seconds.

This question is different to How much can you communicate with your familiar in that that question asks what kind of concepts can be conveyed whereas this question asks how fast those concepts can be explained.