Crypto glossary
Batch auction (coincidence of wants)
A batch auction collects orders over a short period and settles them together at one clearing price, matching opposite trades directly to reduce MEV.
Instead of executing each swap the moment it arrives, a batch auction groups all orders received in a window, for example a few seconds or one block, and settles them in a single transaction. Within a batch every trader of the same pair gets the same price, so the order of transactions inside the batch no longer matters. CoW Protocol is the best-known example in DeFi, with solvers competing to propose the best settlement.
When one user sells ETH for USDC and another buys ETH with USDC in the same batch, they can be matched directly, a coincidence of wants, with no AMM involved and no pool fee. Leftover volume is routed to on-chain liquidity. The design removes the incentive to front-run or sandwich individual orders, since there is no sequence to exploit.
Batching adds a short delay and depends on solvers, which form a small, permissioned group in most systems. Clearing prices may still be worse than a quick swap in a fast-moving market, and direct matches are rare for illiquid tokens.
Example
Two users submit opposite ETH/USDC orders within the same batch; the solver settles them against each other at one price, so neither pays an AMM fee or suffers a sandwich.