OCO Order Placement in Mobile Exchange App

Implementing OCO Order Placement in a Mobile Exchange App

OCO (One-Cancels-the-Other) is a linked pair of limit and stop-limit orders: when one executes, the other is automatically cancelled. Classic use: bought BTC at 40,000, set Take Profit at 45,000 (limit) and Stop Loss at 38,000 (stop-limit). Whichever triggers first, the other disappears.

On Binance API, OCO is a separate endpoint: POST /api/v3/order/oco. It takes seven parameters at once, with its own error logic. The interface should help users fill all seven fields correctly.

OCO Parameters and Their Order

quantity is shared by both orders. This must be clear in the UI: one quantity field, not two.

Price Logic Validation for SELL OCO

On sell: price > currentPrice > stopPrice > stopLimitPrice.

// Android — validating SELL OCO price logic
data class OcoValidationError(val field: String, val message: String)

fun validateOcoSell(
    currentPrice: BigDecimal,
    limitPrice: BigDecimal,
    stopPrice: BigDecimal,
    stopLimitPrice: BigDecimal
): List<OcoValidationError> {
    val errors = mutableListOf<OcoValidationError>()
    if (limitPrice <= currentPrice)
        errors += OcoValidationError("price", "Take Profit must be above current price")
    if (stopPrice >= currentPrice)
        errors += OcoValidationError("stopPrice", "Stop price must be below current price")
    if (stopLimitPrice >= stopPrice)
        errors += OcoValidationError("stopLimitPrice", "Stop limit must be below activation price")
    return errors
}

For BUY OCO, logic is mirrored: stopLimitPrice > stopPrice > currentPrice > price.

UI Concept: One Card — Two Levels

Display OCO as a single card with three price levels on a mini-scale:

▲ Take Profit: 45,000 USDT  (limit order)
│
● Current Price: ~41,500 USDT
│
▼ Stop: 38,500 → Limit: 38,200 USDT  (stop-limit)

Color: green for Take Profit, red for Stop Loss. This reduces cognitive load and order-filling errors.

Cancellation and Statuses

OCO on Binance has orderListId — group ID. When displaying in order history, group both orders under one orderListId. If one executes, the other is marked CANCELED with reason OTHER_SIDE_CANCELED.

WebSocket event: listOrderStatus with type OCO. On ALL_DONE transition — send notification showing which of the two orders triggered.

Timeline: 3–5 days for seven-parameter form, mini-scale price visualization, BUY/SELL logic validation, grouping in order history, push on execution.