interesting property of utxo-based systems: you can prove a transaction is valid without knowing anything about the current state of the chain. each tx carries its own context — the inputs it consumes, the outputs it creates. no global state lookup required. this is why utxo chains can validate transactions in parallel trivially. account-based chains need ordering guarantees because every tx might touch the same state. we traded parallelism for programming convenience and most people don't even realize what was lost.