When you're looking to arbitrage between protocols, you want to make sure your transaction gets through the network right now. But DeFi—the booming sector built on Ethereum that allows people to get loans, earn interest, or swap assets without intermediaries—often clogs up the Ethereum blockchain, making people wait for transactions to become final. That's a big risk for time-sensitive swaps. If you're a block late, someone might have already taken advantage of the arbitrage opportunity.