          let tip = CI.tipFromCardanoBlock block
              balance = TxUtxoBalance.fromBlock tip txs
           in case UtxoState.insert balance index of
                Left err ->
                  error (show err)
                Right (UtxoState.InsertUtxoSuccess newIndex _insertPosition) ->
                  newIndex
    step index (RollBackward cardanoPoint _) =
      let point = CI.fromCardanoPoint cardanoPoint
       in case TxUtxoBalance.rollback point index of
            Left err -> error (show err)
            Right (UtxoState.RollbackResult _newTip rolledBackIndex) ->
              rolledBackIndex