This article focuses on using the Casa Relay as your ethereum relay, and the fees associated with it.
What is a relay?
An ethereum relay is a way to manage interactions with ethereum smart contracts. Casa customers may use Casa, or they may use their ETH Pay Wallet (a separate "single signature" wallet), as a relay for their multi-key vault.
For more information on these two relay types in the Casa app, see Relay types for ethereum vaults.
How does it work?
If a member has opted to use the Casa Relay (rather than the ETH Pay Relay), the Casa wallet will relay transactions and other activity from the the member's vault.
For instance, when a user sends an ETH transaction from their vault, or takes other actions in their vault such as replacing a key, the estimated gas fee is paid to the Casa Relay (note that no fee is paid to the Casa relay during the vault creation, only for actions taken after vault creation; the Casa relay covers the initial cost of the vault creation).
In practice, this means that when you send ETH from your Casa vault, additional ETH (the estimated transaction cost) is immediately sent to the Casa relay's wallet. The Casa relay, being the relay that you selected, pays the network fees on behalf of your vault.
Note that the estimated fee that's sent to the Casa Relay is the fee you pay. The actual cost of the transaction that is paid by the Casa Relay will depend on the current state and activity of the ethereum network, and will rarely be the exact amount of the estimate. The actual amount paid for the transaction as seen on the blockchain may be higher or lower than the fee that was paid to the Casa Relay by the member.
Example transaction
We'll use the following example of how fees may be paid by a Casa member using the Casa relay.
- A transaction for $100 worth of ETH to an external address is created from a Casa multi-key vault.
- Based on current network activity, Casa app estimates that the cost of the fee for the ethereum network will be $5.
- The vault in Casa app pays the $5 worth of ETH to the Casa relay wallet when the transaction is sent.
- The Casa relay pays the actual network fee.
- The transaction is successful, but in this example, the actual cost was $6.
- The Casa member's cost is still just $5.
Conversely, it may also be the case that the transaction ends up costing less than the estimate. In this case, the user still pays the estimated fee to the Casa relay. This means that you are sometimes "underpaying" and sometimes "overpaying" to the Casa relay. We try to make the estimated fee as close as possible to the fee that's likely to be paid to the network.
For any additional questions about the Casa relay, how transaction fees work, or anything else, feel free to reach out.