Decentralized exchanges (DEXes) have experienced rapid growth since 2020, with DEX monthly volume exceeding $162 billion in May 2021. Instead of order books, most DEXes have adopted the automated market maker (AMM) design to bootstrap passive and algorithmic liquidity into liquidity pools. With this approach, liquidity takers can trade against the AMM with any size. To compensate liquidity providers (LPs) for impermanent loss, traders typically pay a fixed fee up to 0.3% distributed proportionally to the amount of liquidity provided by each LP. The trading fee, coupled with gas fees that vary across networks, makes the cost of trading on DEXes much higher than centralized exchanges (CEXes). In contrast, CEXes typically charge no more than 0.1% fee and can be even lower with rebates.