What Is the Main Drawback of Using FOK Orders in Thinly Traded Derivatives Markets?

The main drawback is the high risk of non-execution. Thinly traded derivatives markets have low liquidity and shallow order books, meaning there may not be enough volume available at the desired price to fill the entire FOK order immediately.

Since FOK requires a complete and immediate fill, the order is likely to be cancelled, forcing the trader to break up the order or wait for better market conditions, which can delay the intended trade.