Cancel-Replace Pattern
Cancel-replace lets a market maker amend price, quantity, or order flags without manually issuing separate cancel and place calls.
Why it matters
Separate cancel and place operations can expose a strategy to stale quote risk or temporary loss of queue position. Cancel-replace gives the client one operation with one acknowledgement path.
Replaceable fields
| Field | Replaceable | Notes |
|---|---|---|
| Price | Yes | Must satisfy tick size |
| Quantity | Yes | Must satisfy lot size and collateral checks |
| Time-in-force | Limited | Some transitions require cancel and new order |
| Side | No | Use cancel and new order |
| Market | No | Use cancel and new order |
| Account | No | Use cancel and new order |
Failure behavior
If the replacement is rejected, the original order remains active unless the response explicitly says the original order has been cancelled. Clients must read the final order state from the response before updating local strategy state.
FIX and binary equivalents
- FIX uses OrderCancelReplaceRequest (
35=G). - Binary order entry uses
ReplaceOrder. - HTTP uses the market-maker cancel-replace endpoint in the canonical API reference.