Libbitcoin for Core people

When processing a block, verifying the status of all inputs as unspent is crucial, a task which inherently requires sequential handling due to dependencies between transactions within the same block. This dependency arises because an input in one transaction can be linked to the output of a preceding transaction included in the same block. To validate each transaction, it necessitates a systematic approach where each input's previous output (prevout) must be identified and validated against the unspent transaction outputs (UTXO) set. If the prevout cannot be located within the UTXO set, the transaction fails verification. Following this, every output from the transaction under review needs to be added to the UTXO set. This addition must occur before proceeding to evaluate the next transaction in the block, ensuring the integrity and orderliness of the transaction validation process. This sequence ensures that each transaction is accurately assessed for validity, maintaining the blockchain's coherence and security.