Web3 Wallet App: Transaction Management and Mempool Monitoring for Enhanced User Experience

Managing transactions effectively within a wallet app is crucial to provide users with real-time status updates and control. This article explores advanced techniques for handling pending transactions—including cancellation and acceleration—and leveraging Mempool monitoring to identify stuck transactions.

The Challenge of Low Gas Fees

Wallet apps typically allow users to set custom Gas Fees, enabling cost savings when transaction speed isn’t critical. However, transactions with insufficient Gas Fees may remain pending for extended periods. For example:

• On Etherscan, pending transactions appear in contract transaction lists.
• Lower Gas Prices prolong pending times, sometimes lasting days.
• TxStreet visualizes real-time blockchain activity, showing thousands of pending transactions (e.g., 75,000+ on Ethereum).

👉 Explore real-time blockchain activity on TxStreet

Managing Pending Transactions

To improve UX:

1. Estimate confirmation time: Use Etherscan’s gasestimate API to predict delays.

   • Example: A 20 Gwei Gas Price might take >1 hour to confirm.

2. Prevent Nonce conflicts: Ensure new transactions don’t reuse pending transaction Nonces.

   • Libraries like web3dart automatically fetch correct Nonces via eth_getTransactionCount with pending block parameters.

Canceling or Accelerating Transactions

Canceling Transactions

Send a 0 ETH self-transfer with:

• Same Nonce as the pending transaction.
• 10% higher Gas Fee to avoid "Replacement Transaction Underpriced" errors.

Code Example:

Future sendCancelTransaction({
  required EthPrivateKey privateKey,
  required int nonce,
  required EtherAmount lastGasPrice,
}) async {
  final newGasPrice = lastGasPrice.getInWei * BigInt.from(6) ~/ BigInt.from(5);
  final cancelTx = Transaction(
    from: privateKey.address,
    to: privateKey.address,
    maxFeePerGas: EtherAmount.inWei(newGasPrice),
    value: EtherAmount.zero(),
    nonce: nonce,
  );
  final txHash = await sendRawTransaction(cancelTx);
  return TransactionWithHash(hash: txHash, transaction: cancelTx);
}

Accelerating Transactions

Resend the original transaction with increased Gas Fees.

Monitoring the Mempool

The Mempool (Memory Pool) stores broadcasted but unconfirmed transactions. Key points:

• Miners prioritize transactions from the Mempool based on Gas Prices.
• MEV attacks exploit visible Mempool transactions (e.g., front-running).

Accessing Mempool Data

Services like Blocknative and Quicknode provide APIs to:

1. Monitor pending transactions for specific addresses/contracts.
2. Filter transactions by function calls or sender addresses.

Example: Blocknative Explorer tracks USDT contract transactions in real-time.

FAQs

How can I estimate transaction confirmation time?

Use Etherscan’s gasestimate API with the current Gas Price to predict delays.

What happens if two transactions share the same Nonce?

The transaction with the higher Gas Fee replaces the pending one.

Are there private alternatives to Mempool broadcasting?

Yes, services like Flashbots enable private transactions sent directly to miners.

Conclusion

Effective transaction management—via cancellation/acceleration and Mempool monitoring—significantly enhances wallet app UX. Implement these strategies to give users greater control and transparency.

👉 Learn more about Web3 transaction optimizations

Next: Wallet Connect protocol implementation in wallet apps.

### Keywords:
- Web3 wallet app  
- Transaction management  
- Gas Fee optimization  
- Mempool monitoring  
- Cancel Ethereum transaction  
- Blocknative Explorer  
- MEV attacks