It depends on the size of the withdrawal. Transactions are fully automated and processed within 10-20 minutes normally unless it displays a message on the top of the screen stating manual processing is required. This typically happens when the amounts have exceeded the daily threshold for a specific coin, and those withdrawals can take up to 12-24 hours. This is a security precaution as we don't want the hot wallet to contain too many coins at a time, which could possibly be abused or drained in the unlikely event of unauthorized withdrawals. The thresholds are carefully tuned to what we have observed to be normal behaviour. So basically one user withdrawing a large amount from their holdings could switch the platform into manual withdrawal mode for all users.