Dust Expiry: Clean the UTXO set from spam

In the evolving landscape of cryptocurrency, the mechanism for validating transactions and managing coin ownership is a critical aspect that ensures security and verifiability. A notable point of discussion is the requirement for users to maintain a constantly updated proof to spend their coins, diverging from simpler models such as the SPV (Simplified Payment Verification). This condition necessitates that users either stay online to keep their proofs current or rely on a third party that has validated the chain to provide them with the necessary updated proof. This approach introduces a significant shift from traditional methods where users could transact offline with the assurance of their coin ownership.

The implementation of such a system brings forth several challenges and considerations, particularly in terms of infrastructure and resource requirements. Running an indexer node, which monitors proofs for all coins, emerges as a highly resource-intensive task. Compared to the operational demands of current nodes, this model significantly escalates the costs associated with maintaining the network. Furthermore, it leads to a considerable increase in the bandwidth required for relaying transactions and blocks. While there might be speculation about mitigating these bandwidth demands by maintaining a traditional UTXO (Unspent Transaction Output) set, the necessity to furnish non-local-UTXO peers with proofs complicates this possibility.

This scenario presents a complex trade-off between the enhanced security and verifiability provided by this model and the increased operational demands it imposes. The argument in favor of its eventual necessity is grounded in its asymptotic behavior, suggesting that the benefits of such a system may become more apparent over time. However, the immediate implications and the significant shift in resource requirements make it a topic of debate. It highlights the importance of exploring alternative solutions that balance the trade-offs differently, potentially offering viable paths forward that address these challenges while still ensuring the integrity and reliability of cryptocurrency transactions.