Explain the Role of the ‘Mempool’ in Preventing or Causing Front-Running in DeFi

The mempool (memory pool) is where pending, unconfirmed transactions wait before being included in a block on a blockchain like Ethereum. Since the mempool is public, front-running occurs when a malicious actor sees a profitable pending transaction (e.g. a large swap) and submits their own transaction with a higher gas fee to execute first, causing the original transaction to suffer slippage.

Private relays bypass this public mempool.