What Is Maximal Extractable Value (MEV) & How Does It Work?

All new transactions on a blockchain are verified through the work of miners or validators. They must be rewarded for their hard work, as well as for their use of required resources, and they will logically give preference to user transactions that offer greater compensation. This means that higher transaction fees and block rewards often result in those transactions being completed faster. To further optimize profits, block producers may strategically manipulate the system. Collectively, these strategies are referred to as maximal extractable value.

Key Takeaways:

• Maximal extractable value (MEV) refers to a strategy by which miners, validators and searchers insert, censor and reorder transactions to optimize their profitability.
• While MEV strategies can be advantageous for block producers, they can have negative consequences for users and networks.
• Some of the most common MEV strategies include DEX arbitrage, back-running, front-running, liquidation and sandwich trading.

What Is Maximal Extractable Value (MEV)?

Maximal extractable value (MEV) is a strategy that miners, validators and searchers use to optimize their profitability by inserting, censoring and reordering transactions. While MEV reflects profits for them, it has negative consequences for users and networks.

The term “maximal extractable value,” or MEV, first came to light in 2021, but it has actually been used in blockchain transactions for far longer. MEV originally referred to “miner extractable value” because it describes the extra value that is strategically available to miners on a proof of work (PoW) network through transaction fees and block rewards. More specifically, the added value comes from ordering, including and excluding transactions in a block. Today, however, many networks use a proof of stake (PoS) system rather than PoW. The tasks completed by miners in a PoW environment are completed by validators in a PoS environment. For this reason, MEV now means maximal extractable value. 

Ethereum is among the most dominant DeFi ecosystems, so it’s most commonly associated with MEV. Ethereum’s transition from PoW to PoS in the Merge resulted in this change in the acronym’s wording.

How Does MEV Work?

Block producers have full discretion over reordering, including and excluding transactions through their efforts. The orders with the highest transaction fees are selected by the block producers first so that they can optimize profits. Because they’re fully responsible for how they produce blocks, they can manipulate placement to optimize their return through various MEV strategies. One of the many strategies they can use involves identifying a large transaction that may impact the value of a specific cryptocurrency. 

By placing orders both directly in front of and behind that large transaction, they can profit from the expected price increase. While this and other MEV strategies are profitable for block producers, they have negative consequences for blockchain users. One of these consequences is inflated gas fees. MEV may also destabilize a blockchain network and have other negative effects.

MEV Searchers

With proof of work consensus, miners extracted roughly 60% of MEV profits. The remaining MEV revenue went to MEV searchers. Searchers continue to be involved in PoS blockchains. They look for extractable value on the blockchain, often paying high gas fees to extract maximum value from transactions. In fact, searchers may pay gas fees of more than 90% of their income to ensure the profitability of specific transactions. 

Searchers can profit by reviewing transactions and strategically grouping them together in bundles. These bundles may also include other transactions in the mempool, and the bundled transactions can then be executed in a specific sequence. Often, they utilize complex algorithms executed by bots.

There are several strategies that searchers may use to extract a profit. They can utilize bots to scour pending transactions, generally focusing on larger transactions. In addition to using these MEV strategies, searchers have used priority gas auctions, or PGAs, which essentially involve bidding up gas fees through the use of arbitrage transactions. 

Unfortunately, PGAs have brought many negative outcomes. For example, failed attempts took up block space that others could have used. By spamming transactions, node operators’ loads increased. There were also huge gas price fluctuations, and miners not using searchers were at a competitive advantage.

Common MEV Strategies

There are numerous ways to optimize MEV extraction. Searchers and bots actively review pending transactions to identify opportunities that are ripe for value extraction. Each of these MEV strategies is utilized in specific scenarios. In addition to the strategies mentioned below, rarer gambits like uncle bandit attacks and time bandit attacks may be used when specific situations are presented. Let’s look at the more common MEV strategies that are used.

DEX Arbitrage

Of all the MEV strategies, DEX arbitrage is the most common, whereby bots actively monitor prices on many exchanges. When they detect a differential in pricing across exchanges, they conduct trades to capitalize accordingly. By simply conducting transaction reordering or order insertion, additional profits may be generated through the price differential. 

However, the impact of arbitrage on other traders is negative. This is because the bots quickly bid up gas fees to ensure profitability, making trades less profitable for other traders. Slippage may also affect users' trading activities.

Back-Running

With back-running, a bot is used to look for token pair listings that present opportunities for profits. When a pair is identified, the bot moves a pending transaction directly between the pair listing. This enables it to have priority over others when purchasing tokens. Other traders will only have access to the tokens that the bot didn’t buy. After the purchase, the bot holds the tokens until they’ve appreciated in value to a certain level, and then the tokens are sold to generate a profit.

Front-Running

Bots may also use an MEV strategy known as front-running. If a large trade is detected by a bot, the bot copies the trade and adds a higher gas fee to it. By doing so, it gives that large trade a higher placement than others in the queue. As a result, the price of the digital asset being purchased increases. This creates additional profit when the digital asset is later sold.

Liquidation

This MEV strategy is used by searchers as well as block producers. Users are now able to borrow against their digital assets, and this leverage may provide them with opportunities for additional gains. In the event that the value of a collateralized asset falls below a predetermined price, the collateral is liquidated to mitigate losses for the lenders. Rewards may be paid for the transactions that cause the value to fall and the liquidation to be executed. Bots are used to identify high-risk leveraged positions, and they strategically liquidate other users’ collateral and pay off the lenders. By doing so, the searchers may receive the protocol reward. In some cases, they may be able to purchase the assets that they liquidate at a discount. This enables them to then quickly sell the assets for a profit.

Sandwich Trading

Sandwich trading, also referred to as a sandwich attack or sandwiching, is an MEV strategy in which two bots are used to essentially surround a targeted transaction. A large transaction has the potential to move a token’s price. Therefore, the bots are used — one to place an order before the large transaction, and another order after the transaction. By doing so, the searcher can exploit the transaction to generate a profit.

NFT MEV

MEV strategies can also be used with NFTs. Searchers can scour the NFT market for lucrative opportunities and utilize bots to execute those transactions. For example, they may identify an NFT that’s priced below market value. By knowing the true value of the NFT, they can often outbid others. In some instances, searchers have purchased entire NFT collections at the base price to take advantage of reselling opportunities.

Advantages of MEV

Maximal extraction value is a reasonable product of block validation because producers understandably want to optimize their gains. While the attention is often on how MEV negatively impacts other users and the network, there are a few key advantages to consider as well. 

Rewards Miners and Validators

Block producers serve an essential purpose on Ethereum and other blockchains. The blockchains simply cannot function without their efforts to verify transactions. However, their services aren’t available for free. Gas fees and other incentives are used to reward them for their efforts. In many cases, this is how block producers earn their living. 

The fees are also essential for purchasing the powerful machines required to mine a block. More than that, these fees and incentives can actually be used to promote faster transaction processing, providing users with a way to manipulate the placement of their transactions for faster processing.

Ethereum PoS Validators

Ethereum’s PoS consensus allows any user who stakes 32 ETH to create a node and become a validator. Previously, with PoW, this wasn’t possible. But users with enough ETH can now take advantage of MEV profits. While this possibility is available to far more users than it once was, it’s important to note that MEV still requires exceptional skill. Some users who have enough tokens to stake may not have the technological expertise required.

Corrects System Inefficiencies

As a result of MEV, block producers and searchers can improve the system by correcting inefficiencies. For example, price corrections can be made quickly through their focus on arbitrage opportunities. In addition, their efforts identify riskier loans, and help lenders recoup their assets on these loans sooner. MEV is often viewed as having negative consequences for users, but it benefits other users in various ways.

Disadvantages of MEV

While MEV has its advantages, it also creates several problematic issues. In fact, as early as 2014, significant flaws of MEV were known. These disadvantages impact other blockchain users, as well as the blockchain itself. 

Network Destabilization and Congestion

Because block producers have full control over the ordering and inclusion of transactions, they can draw power from users without their knowledge. This may impact users’ confidence in placing transactions on the blockchain. MEV also adds extra transactions to the network, which results in network congestion. As a result, slippage may be more of a problem. Destabilization may also be a concern if reordering the previous block’s transactions is more profitable than working on the next block.

Diminished User Experience

Some MEV opportunities, including sandwiching and front-running, result in escalating transaction prices and slower processing of other users’ transactions. As a result, some users may overpay for their transactions, resulting in decreased profitability. In addition, by adjusting the ordering of transactions, slippage can also impact the profitability of some transactions.

It’s important to note that some of the impacts of MEV can be avoided. For example, DApp users can place off-chain trade orders with specified order preferences. By placing all orders in a single batch, all transactions have the same price. This eliminates the financial gain that’s otherwise available from reordering transactions.

MEV on PoW vs. MEV on PoS

When Ethereum operated using a PoW consensus, miners had full control of the selection of transactions and their aggregation into blocks. They alone decided in which order to process pending transactions. Because the system was designed to optimize miners’ profits, selection and transaction ordering naturally gave preference to transactions with higher fees. That’s why MEV meant “miner extractable value.”

On Sep 15, 2022, Ethereum completed its migration from PoW to PoS in what is referred to as the Merge. Post-Merge, validators now do the work that miners did with PoW. They are responsible for authenticating transactions, and they receive rewards for doing so. Hence, MEV now means “maximal extractable value” and applies to all block producers, rather than only to miners. 

The Future of MEV

MEV serves an essential role in the functionality of blockchains via the process of validating transactions. However, it’s well-known that significant disadvantages must be addressed. As mentioned, some of the negative effects of MEV can be bypassed when DApp users place off-chain trade orders. Some blockchains have addressed MEV’s problems. For example, Chainlink uses FSS, or Fair Sequencing Services. FSS promotes predictability and equitability in time ranking. It also leverages Layer 2 rollups to sort and scale transactions.

MEV continues to impact blockchains and their users. Thus far, there are limited strategies available for users to mitigate the full effects of MEV. At the same time, only select blockchains have implemented protocols to ensure that manipulation by block producers and searchers doesn’t negatively affect other users. With this in mind, MEV will continue to be a hot topic in the industry, and more comprehensive strategies must be identified and implemented to block providers from profiting without negative consequences.

The Bottom Line

Blockchain providers strategically and financially benefit from maximal extraction value strategies, but their actions have negative ramifications for networks and their users. Improvements are necessary to ensure that networks can continue to function efficiently and fairly for all involved.

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