Have to break through the 110 put interest first. A large open put interest can act like a magnet but typically it is a contrarian indicator. If I short a spy oct 100 put right now, I would be doing so because I either think we stay above it and I capture the premium or I think that spy is a buy at 100 and if that put gets exercised the the underlying gets put to me at that strike and my cost is 100 - any premium I made selling it. Retail players are the majority that are going long the option while pros are the mostly the ones selling premium. If you are looking for a selloff, look for one when spy is trading above where the largest open call interest is, and if looking for a rally, look for spy to be trading under where the largest open put interest is. right now oct spy interest to me indicates we can trade 110-116. This is not set in stone and one of the favorite games to be played is to run it past the strike to suck in more premium before jamming it the other way. The expanded range is 109 - 117.
Thanks for the explanation, I was thinking it could be someone trying to capture some premium also but wasn't sure. Does the price usually get pinned between the highest open interests on the call and put side at the expiration?