I don't think you understand the concept of FIFO. It is used as a queue, and is pretty standard practice in the real stock and futures exchanges. This is to prevent any kind of favor in hitting the filling of the order. If you place an limit order at 1.000 first, and the next guy puts in the order after you at the same 1.000 price. Then you order will be filled first because you are first in. Same as stops, first out.

This mostly is introduced to prevent the market makers from hitting their own orders while bypassing others. This prevents cheating by the market maker.

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