  This work aims to address the general order manipulation issue in
blockchain-based decentralized exchanges (DEX) by exploring the benefits of
employing a novel combination of order-fair atomic broadcast (of-ABC)
mechanisms for transaction ordering and frequent batch auction (FBA) for
breaking the order while executing those transactions. In of-ABC, transactions
submitted to a sufficient number of blockchain validators are ordered before or
along with later transactions. FBA then executes transactions with a uniform
price double auction that prioritizes price instead of transaction order within
the same committed batch.
  To demonstrate the merits of our order-but-not-execute-in-order design, we
compare the welfare loss and liquidity provision in DEX under FBA and its
continuous counterpart, the Continuous Limit Order Book (CLOB). Assuming that
the exchange is realized over an of-ABC protocol, we find that (1) FBA always
achieves better social welfare when no party is privately informed about asset
valuations. Even otherwise, FBA incurs less welfare loss compared to CLOB when
(2) price takers and public information reflecting asset value changes arrives
sufficiently frequently compared to private information, or (3) the priority
fees are small, or (4) the market is more balanced on both sides. Our empirical
analysis on dYdX transactions indicates additional $8\%-83\%$ costs when
transactions are executed continuously. Further, our findings also indicate
that liquidity provision is better under FBA under similar conditions.
