BitMEX fills orders using price-time priority. The best-priced orders execute first. Among orders at the same price, the earliest-submitted order fills first. Amending order price or increasing quantity sends the order to the back of the queue. Decreasing quantity preserves queue position.
How Does Price-Time Priority Work on BitMEX?
Orders on BitMEX are filled using price-time priority. This means two factors determine execution order:
- Price: Orders at a better price (higher for bids, lower for asks) always execute before orders at worse prices.
- Time: Among orders at the same price level, the order submitted earliest fills first.
This is the standard matching engine logic used by most major exchanges and ensures fair, deterministic order execution.
What Happens to Queue Priority When I Amend an Order?
Amending an order on BitMEX can affect its position in the queue.
- Amending the order price: The order loses its queue position and moves to the back of the queue at the new price level.
- Increasing order quantity: The order loses its queue position and moves to the back of the queue.
- Decreasing order quantity: The order retains its existing queue position.
This means traders who want to maintain queue priority should avoid changing price or increasing size on existing orders. If you need a better price, cancelling and resubmitting may produce the same result as amending, since both actions place the order at the back of the queue.