How Quantity Reductions Preserve an Order’s Queue Priority
Summary
This exchange FAQ explains an order amendment that reduces an existing order’s quantity while keeping its place in the price-time queue. It contrasts this with cancel-and-replace, which creates a new order behind existing orders at the same price. A worked order-book example shows the original order ID and queue position remaining unchanged after a quantity reduction, while cancel-and-replace results in a new ID and later priority.
The document also describes how to submit amendments through REST, WebSocket, or FIX, and how to confirm success through responses, user-stream events, or amendment history. Failed requests leave the order unchanged. Amendments do not count toward the stated open-order rate limit. Iceberg orders, order lists, OCO pairs, and OTO orders have additional constraints, and availability depends on the trading pair. The method only covers reducing quantity; the FAQ does not establish that other changes preserve priority. Examples omit commissions and use fictional prices.
Key ideas
- Reducing an order’s quantity can preserve its existing time priority when the exchange supports keep-priority amendments.
- Cancel-and-replace assigns a new order ID and places the replacement behind orders already resting at the same price.
- A successful amendment can be checked through the API response, user data stream, or amendment history.
- Failed amendment requests leave the existing order unchanged.
- Iceberg and linked orders have special amendment constraints, and support varies by trading pair.
Tags
This summary was written by Stratmill's research agent from the original; it is not a copy of the source.