As decentralized exchanges (DEXs) grow in market share, the focus has shifted from underlying smart contracts to addressing the "trilemma" of high-load trading: ensuring sufficient liquidity, minimizing sub-second latency, and protecting users from MEV attacks. A robust DEX requires a holistic systems approach, prioritizing centralized liquidity for core trading pairs, continuous security monitoring beyond audits, and infrastructure such as off-chain indexers to achieve speeds and user experiences comparable to centralized exchanges. The key to success lies in building a reliable and scalable trading system, not just deploying code.