principlejavascriptMajor
MEV awareness: protecting transactions from frontrunning and sandwich attacks
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Flashbots Protect RPC
MEVfrontrunningsandwich attackFlashbotsslippageprivate mempool
Problem
Mempool transactions are visible to MEV bots that can frontrun or sandwich them, extracting value from users of DEXes and other DeFi protocols.
Solution
Use a tight slippage tolerance, submit transactions through Flashbots Protect RPC or MEV Blocker to bypass the public mempool, and use commit-reveal schemes for sensitive operations.
// Use MEV-protected RPC endpoint
const provider = new ethers.JsonRpcProvider('https://rpc.flashbots.net');Why
The public mempool is a competitive space where searchers monitor for profitable opportunities. Private RPCs route transactions directly to block builders, bypassing mempool exposure.
Gotchas
- Private RPCs like Flashbots Protect may have higher latency or fail to include transactions during congestion
- Even with slippage protection, large orders on DEXes with thin liquidity will have high price impact
- Commit-reveal patterns add latency (two transactions) but fully prevent frontrunning of the revealed value
Code Snippets
Use Flashbots Protect RPC to avoid MEV
import { ethers } from 'ethers';
// Route transactions through Flashbots Protect (skips public mempool)
const provider = new ethers.JsonRpcProvider('https://rpc.flashbots.net');
const signer = new ethers.Wallet(privateKey, provider);
// For Uniswap swaps, always set amountOutMinimum to enforce slippage
const params = {
tokenIn: WETH,
tokenOut: USDC,
fee: 3000,
recipient: signer.address,
amountIn: ethers.parseEther('1'),
amountOutMinimum: expectedOut * 995n / 1000n, // 0.5% max slippage
sqrtPriceLimitX96: 0n,
};Context
Building or using DeFi protocols where transaction value can be extracted by bots
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