How Idempotency Keys Prevent Duplicate Orders From Repeated Button Taps

When a stock-trading app responds slowly, frustrated users may tap the Buy button multiple times, risking duplicate orders being placed. Disabling the button on the client side is insufficient, as multiple tap events can be processed before the UI visibly updates. Idempotency — the principle that an operation performed multiple times produces the same result as performing it once — offers a more reliable solution. The approach requires the client to generate a unique idempotency key tied to a specific user intent, reusing that same key for any retries rather than creating a new one each time. The server must then recognize repeated requests sharing that key and process the underlying order only once, making idempotency an end-to-end contract between client and server.