SPY options are American-style, which means the holder can exercise any time before expiration, not just at the end. For anyone who has sold an option, that creates early-assignment risk: the buyer exercises, and you're assigned — forced to deliver — before you expected to be.

Who's exposed (and who isn't)

Only the short side can be assigned. If you're long a single option, you're immune. But if you trade spreads, one leg is short — so spread traders do carry early-assignment risk on that leg.

When it actually happens

Early exercise is usually irrational for the buyer (it throws away remaining time value), so it's rare — except in two cases. Deep in-the-money short options with little time value left are prime candidates, because there's almost no premium being surrendered. And short calls around an ex-dividend date can be exercised so the buyer captures the dividend. Both are worth watching if you're short those strikes.

Early assignment is a seller's tail risk, concentrated in deep-ITM shorts and dividend-dated calls. Buyers can ignore it entirely.

What to do about it

If you sell spreads, keep an eye on any short leg that goes deep ITM or approaches an ex-dividend date, and consider closing or rolling before it's exercised on you. If early assignment does hit, you'll wake up with a stock position and the other leg still open — manageable, but only if you're not surprised. For pure long-scalp trades through NoVo, this risk simply doesn't arise.