Shortest lag time before airlock activity

I brewed today and pitched at a temp slightly on the high side. So I put my primary in my beer fridge to bring down the temp a few more degrees. I just checked and there is airlock activity just 2 hrs after pitching. Is this just activity caused by the warmer air in the primary escaping because the wort temp is higher than the ambient temp in the fridge?

Could there be fermentation activity just 2 hrs after pitching?

As the wort cools, it will actually suck air back into the beer. Are you sure the air is escaping and not entering?

Maybe. Don’t worry too much about your airlock. Just let it ride for a couple of weeks and see how it’s doing then.

It is certainly not impossible.
I brewed a big barleywine just two days ago and pitched 50% of a very recently harvested yeast cake (it was very freshly harvested from another brew). I had bubbling and a rocky krausen starting to build within 90 minutes.
I’d say that your slightly high temps combined with what were presumably healthy yeasties could absolutelty result in such a quick takeoff.

My experience of two days ago wasn’t typical, but its definitely not the first time it has ever gone down that way, either.