Doesn't coinpayments lock the rate for like 6 hours? 15 minutes sounds very short especially if the transaction has to confirm within that timespan.
For coinpayments the fixed rate lasts for 8 hours I only knew this because I bought a monthly subscription from a certain service.
My local exchange only gives me a small window of like 20-30 minutes but I think even if the transaction fails to confirm they'll still use the same rates.
Sorry if I'm being too noob, but what if I don't want to overpay or underpay as a result of floating exchange rate? Especially if we're talking about specific amount of coins. I just can\t understand why those details doesn't matter.
It depends on the situation, if you're only exchanging cryptocurrencies from specific exchanges like changelly or coinswitch that have limited time windows it doesn't matter because others would prefer to receive their converted coins in a few minutes rather than waiting longer for such minimal price difference.