ETH transactions can get stuck due to insufficient gas fees or sudden spikes in network congestion. When the gas fee provided is too low compared to the current network demand, validators may prioritize other transactions with higher fees, causing your transaction to remain unprocessed in the mempool. This can lead to delays and a backlog of subsequent transactions, especially if they depend on the completion of the stuck transaction. Managing gas fees and monitoring network conditions are crucial to prevent transactions from getting stuck. Replace By Fee (RBF) and Child Pays For Parent (CPFP) are mechanisms used to expedite stuck transactions on blockchain networks.

• RBF - commonly used in Ethereum and other EVM-based networks, allows a sender to replace a pending transaction with a new one that has a higher gas fee, increasing the likelihood of it being processed promptly.
• Drop EVM transaction - uses RBF to replace the original transaction with a new transaction of 0 value, and a destination identical to the source, effectively canceling the transfer.
• CPFP - primarily used in Bitcoin, involves creating a new transaction (the child) that pays a higher fee, incentivizing miners to also confirm the original stuck transaction (the parent) due to the combined higher fee.

Both RBF and CPFP methods aim to prioritize the processing of transactions that might otherwise remain stuck due to low fees or network congestion.

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RBF and CPFP in Fireblocks

Fireblocks customers can boost or drop their stuck transactions using the following methods:

• Clicking the “Boost” icon on the Transaction card in the Fireblocks Web Console. For more information on the process and the availability of the boosting operation, refer to this guide.
• Using the Fireblocks API for the following scenarios:
  • Perform RBF for a stuck EVM transaction
  • Drop a stuck EVM transaction
  • Perform CPFP for a stuck BTC transaction