Most traders only use market and limit orders. But your broker offers time-in-force and fill conditions that control how an order is filled — and on wider, thinner options they matter more than you'd think.

The three conditions

IOC — Immediate-or-Cancel. Fill whatever is available right now at your price, and cancel the rest instantly. You might get a partial fill. Good for grabbing available liquidity without leaving a resting order hanging.
FOK — Fill-or-Kill. Fill the entire order immediately or cancel all of it. No partials, no waiting. Use it when a partial position is worse than none.
AON — All-or-None. Fill the full size or don't fill — but unlike FOK, it's willing to wait for the whole quantity. You avoid partials at the cost of maybe not filling for a while.

Plain limit orders can fill piecemeal. These conditions let you say “all of it, or none” — which on a thin strike is often what you actually want.

When they help

On liquid, near-the-money SPY strikes you'll rarely need them — there's enough size to fill a normal limit cleanly. They earn their keep on thinner, wider strikes, where a plain limit can fill in awkward pieces at drifting prices. FOK or AON keeps you from ending up with a half-position you didn't want; IOC lets you take what's there and move on. For fast scalping, though, the deeper fix is to trade liquid strikes in the first place — and to let your platform route the order. Also mind your time-in-force so a working order doesn't outlive the session.