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What is Ethereum Mempool?

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In blockchain terminologies, we often come across a term called a mempool. A mempool or a memory pool is basically a waiting area for pending transactions. This article focuses on discussing mempool in Ethereum. The following topics will be discussed here:

  1. What is Ethereum Mempool?
  2. What is the Use of Ethereum Mempool?
  3. How Does the Mempool Work? 
  4. How Does Mempool Effects Transaction Fees?
  5. How To Speed Up Bitcoin Transactions?
  6. How To Speed Up An Ethereum Transaction?

Let’s discuss each of these topics in detail.

What is Ethereum Mempool?

It is the gateway to Ethereum’s blockchain. When an Ethereum node receives a transaction, it is not instantly added to a block. The transaction is held in a waiting area or a buffer zone.

  • The transaction goes from a number of levels of verification such as it checks whether the output is greater than the input, whether the signature is valid or not, etc., and then only it is added to a block.
  • The transaction is not added to a block if it fails any of these validations or checks given above.
  • The role of a mempool comes while a transaction is going through these checks. It is simply kept in this waiting area or a mempool.
  • As soon as the transaction confirms, it is removed from the mempool and added to a block.

Mempool is not a master reference shared universally by all nodes. There’s no “one” mempool. This means each node configures its own rules for the node’s mempool. In fact, a node can be the first to receive a transaction but it is possible that it might not have propagated the transaction to the rest of the network.

What is the use of Ethereum Mempool?

A mempool is the core component of how a blockchain moves transactions from a user’s wallet to confirmation in a block. A blockchain creates a permanent collection of transactions, so once it is written, it can’t be unwritten. So, a mechanism is needed to figure out the order of transactions to be added to a block. Below are some of the reasons why mempool is needed:

  • Transaction ordering: The important tasks such as transaction ordering, block construction, and transaction fee prioritization are all enabled by the mempool.
  • Store lower gas prices transactions: Since transactions need to be stored before they are confirmed and added to a block, usually, the transactions with lower gas prices (the fee is known as gas) spend more time in a mempool. These types of transactions are overwritten with replacement transactions or ‘cancel and speed up transaction’. 
  • Getting pending transactions: One of the uses of the Mempool includes getting pending transactions to obtain trading prices on DEX, analyze the gas prices, adjust the transaction price to avoid getting dropped, and reduce rejection rates by analyzing and simulating pending transactions

How Does the Mempool Work?

Below are the steps to show how mempool works:

  1. When a user makes a transaction, it is sent to a node or nodes that it is connected to. 
  2. Then a node validates some checks on it ( it checks whether the output is greater than the input, whether the signature is valid or not, etc), adding it to its own mempool. 
  3. The node sends it to the next node and the next node again adds it to its own mempool and broadcasts it to its peers.
  4. Each node that receives the transaction will repeat the process and replicate the transaction across the network.
  5. Some of these are mining nodes that add it to a block and then compete to solve a hash of the block to be the one to add it to the blockchain. 
  6. Once a miner is successful and the block of transactions is added to the chain, and the new block is broadcasted back across the network.
  7. All the nodes receive the newly added block and can see the included transactions. If they have any of these mined transactions added to their mempool then the nodes will remove them from the mempool.

How the Mempool Effects Transaction Fees?

Bitcoin transactions involve the process called mining. Because an extra effort is required by the miners for this process, the Bitcoin transactions charge an extra fee called the transaction fee. Paying more fees can help you get the transaction confirmed quicker. There’s no official transaction fee required, but miners prioritize transactions with a fee since it increases their reward per block.

  • A mempool’s size depends on the node. The default size of 300 MB. When a node is near its RAM limit then it will set a minimum fee rate and communicates this to its peers so that they don’t forward transactions below this rate until the RAM doesn’t clear some memory.
  • A node with a small or large mempool may drop the transactions earlier or later which results in differing mempool sizes. 
  • This causes congestion and at this point, users can either wait for the congestion to clear, or they can pay higher fees to get their transactions pushed through faster.  
  • Since there is no financial incentive for running a node the hardware that is dedicated to it is limited and so a node’s Mempool often max out its RAM (it is 300MBs by default). When this happens the node just crashes and restarts with an empty Mempool.

How to Speed Up Bitcoin Transactions?

The main factors that influence the period of a Bitcoin transaction are:

  1. Transaction fees
  2. Network activity
  3. Hash rate
  4. Network attacks

It won’t be possible to speed up the bitcoin transactions if the previous transaction still remains within the mempool (they may not have been yet confirmed). Also, Bitcoin transactions can’t be confirmed unless all previous transactions have been confirmed.

Depending on what the blockchain wallet supports, there are two methods to speed up the bitcoin transaction:

  1. Opt-in Replace-by-Fee (RBF): If supported by the wallet, there might be the choice of an opt-in Replace-by-Fee (RBF) which lets the user resend the transaction replacing the lower fee with a higher fee so that it is more attractive to the miner to speed it up.
  2. Child Pays For Parent (CPFP): If the wallet doesn’t support RBF, then the user might have the choice of the “child pays for parent” (CPFP) technique. The procedure is simple to broadcast a new transaction (called a child transaction) using the change (unspent output) from the original parent transaction, but with a much higher fee.    

Other than this, one can use accelerators such as BTC Nitro. It works by reminding the miners about the transaction. The transaction is rebroadcasted to several Bitcoin nodes and then re-queued to speed up the confirmation process. If the user uses the accelerator for free, the transaction will be prioritized, but not as high as it would be via the paid service. In order to prioritize the transaction with the help of an accelerator, the user will have to enter the unique transaction ID, also known as a hash ID, for the miners to recognize which transaction is to be speed up. There is no guarantee that the transaction will be prioritized when using a Bitcoin transaction accelerator.

The transaction could still be pending because:

  • The transaction is still in the process.
  • The transaction probably failed.
  • The transaction was sent to an incorrect address.
  • The transaction might involve another Blockchain.

How to Speed Up an Ethereum Transaction?

In the Ethereum blockchain network, the transaction fees are known as gas. There are three ways to speed up the Ethereum transaction:

  • Wait and See: To speed up an Ethereum Transaction wait for the congestion to ease up and then get the transaction accepted.
  • Speed up by adding gas: The user can add gas and get the transaction speed up. This is an attempt to speed up the validation of a pending transaction.
  • Cancel the transaction and try again: One can simply cancel the transaction and try again later. The cancellation will overwrite with a zero value.

The best solution to get the transaction validated in a timely manner is to pay a fair transaction fee on the first attempt of the transaction. 

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Last Updated : 28 Mar, 2023
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