COSS puts security above convenience, and we hope our users appreciate that. There are multiple transactions in play that a user doesn't see when depositing and withdrawing as we store all cryptocurrencies offline. So please allow some time for transactions to clear. That is not optimal for instant traders looking for arbitrage, but we will not compromise security over convenience in this matter. 10-30 minutes on most ERC20 tokens and 1-3 hours for BTC as a general rule (but with exceptions both ways).