The Predator Playground of the Public Mempool
When you execute a token swap on a decentralized exchange like Uniswap, SushiSwap, or PancakeSwap, your transaction is not added to a block immediately. Instead, it sits in the Ethereum Public Mempool—a transparent waiting room visible to high-frequency trading algorithms known as Maximal Extractable Value (MEV) Searchers.
Anatomy of an MEV Sandwich Attack
If you execute a large trade with a loose slippage tolerance (e.g., 2% to 5%), an MEV bot executes three coordinated steps within the exact same block:
- Front-Run Buy: The bot pays a higher gas fee (priority fee) to insert its own purchase transaction before your trade, driving up the pool price.
- Victim Swap: Your trade executes at the worst possible price permitted by your slippage tolerance.
- Back-Run Sell: The bot immediately sells its tokens at the inflated price, extracting pure profit while leaving you with fewer tokens than anticipated.
How Private RPCs (Flashbots Protect & MEVBlocker) Neutralize Bots
By routing your MetaMask transactions through private RPC endpoints (like https://rpc.flashbots.net or https://rpc.mevblocker.io), your pending swap bypasses the public mempool completely and is delivered directly to trusted block builders.
For more on Web3 RPC privacy, review our guide on how default RPCs log IP addresses during transactions.
Audit your network connection and inspect your outward IP metadata on our free Web3 network inspector.