Abstract: Methods, systems, and apparatuses, including computer programs encoded on computer-readable media, for requesting one or more open orders from a trading platform and sending to a client. Price data for at least one of the one or more orders is requested and sent to the client. A limit price for a first open order from the one or more open orders is received and a new order request is built. The order request is based at least on the first open order and the limit price. A cancel order request is built based at least on the first open order. A cancel-replace request is send to the trading platform. The cancel-replace request is based at least on the new order request and the cancel order request. The trading platform cancels an open order and opens a new order based on the cancel-replace request.

Abstract: Methods, systems, and apparatuses, including computer programs encoded on computer-readable media, for receiving a create order request from a client. Building a fill order request based on the create order request and comprising a security identifier and a quantity. Extracting a conditional order price from the create order request. Building a conditional order request based on the fill order request and the conditional order price. Sending an open order request to the trading platform, the open order request comprising the fill order request and the conditional order request, wherein the trading platform creates a fill order and a conditional order based on the open order request.