What Is “Front-Running” and How Is It Exacerbated by a Large Mempool?

Front-running is a malicious practice where an entity observes a pending transaction and executes their own transaction ahead of it to profit from the expected price movement. A large, visible mempool makes it easier for front-running bots to scan for high-value pending transactions (like large DEX swaps or liquidations).

They then bid a higher gas fee to ensure their transaction is included in the block before the victim's, exacerbating the problem.