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What is the mempool, what is MEV, and why do these two concepts — largely invisible to everyday users — shape the economics of almost every transaction on Ethereum and many other blockchains? In this episode of Crypto for Beginners, we pull back the curtain on how blockchain transactions actually get processed, and explain why a hidden war for profits is being fought inside every block.
The mempool — short for memory pool — is the waiting room for unconfirmed blockchain transactions. When you send a transaction on Ethereum, it does not go directly into a block. It is first broadcast to the network and held in the mempool, waiting to be picked up by a validator and included in the next block. Transactions in the mempool are publicly visible to everyone. This public visibility is the key to understanding MEV.
MEV stands for Maximal Extractable Value — formerly called Miner Extractable Value. It refers to the profit that block producers can extract by choosing which transactions to include in a block, in what order, and by inserting their own transactions. Because the mempool is public, sophisticated actors called searchers can watch for profitable opportunities and act on them before regular users. The three most common forms of MEV are arbitrage — exploiting price differences between DEXes — sandwich attacks — where a searcher places trades directly before and after a large user trade to profit from the price impact — and liquidations — racing to liquidate undercollateralised positions on lending protocols for a reward.
MEV is not a small phenomenon. Hundreds of millions of dollars have been extracted from Ethereum users through MEV, often without their knowledge. A sandwich attack can cost a typical DeFi user 0.5–2% on a large swap — invisible but real. Flashbots, launched in 2021, introduced MEV-Boost, a system that makes MEV extraction more transparent and efficient by creating a marketplace between searchers and validators. While this did not eliminate MEV, it made the process more orderly and reduced the most harmful forms of spam that were clogging the network.
In 2026, MEV-Boost is used by the vast majority of Ethereum validators. Encrypted mempools and fair ordering protocols are active research areas aimed at protecting users from harmful MEV. Understanding the mempool and MEV is essential for any serious DeFi participant.
Topics covered: mempool explained for beginners, what is MEV crypto, Maximal Extractable Value Ethereum, sandwich attack DeFi explained, MEV-Boost Flashbots Ethereum, how blockchain transactions are ordered, arbitrage MEV bots, liquidation MEV DeFi, protect against MEV sandwich attack, Ethereum validator MEV revenue, cryptocurrency for beginners This episode is essential listening for anyone who wants to build real knowledge about the crypto space — not just price speculation, but the deeper forces shaping which projects survive and which ones fade. Whether you are a complete beginner taking your first steps into digital assets, or an experienced investor looking to sharpen your understanding, Crypto for Beginners is designed to give you the foundational knowledge and critical thinking tools you need. Subscribe and follow the show for new episodes every week covering the most important cryptocurrencies, protocols, technologies, and trends shaping the future of decentralised finance, Web3, and the broader digital economy in 2026 and beyond.
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