When a customer pays in crypto, the merchant shows an amount in a coin that is priced against a fiat currency. Prices move, so the quote cannot stay valid forever. Most gateways handle this with a price-lock window: the quoted amount is honoured for a fixed number of minutes, then expires. If you are integrating a gateway into your own checkout, you still need to reflect that window correctly in your order logic and UI.

The data you need per quote

{ "order_id" : "A-10293" , "fiat_amount" : "49.00" , "fiat_currency" : "USD" , "crypto_amount" : "49.12" , "crypto_currency" : "USDT" , "network" : "TRC20" , "quote_created_at" : "2026-10-30T02:10:00Z" , "quote_expires_at" : "2026-10-30T02:25:00Z" }

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Store the expiry from the gateway response.…