Google Apps Script Rhino vs V8 Performance (343ms v 45,042ms)

I created a google apps script deployed as a web app executed as "user_deploying" and accessible by "anyone_anonymos". Executing this with Rhino takes 343ms and executing this with V8 takes 45,042ms, as calculated at the Marks in the below code. Why the difference and how can I increase the performance of V8, specifically Mark II?

Execution time averages in ms (rhino/V8):

• 227/497 Mark I - Jdbc.getCloudSqlConnection()
• 112/44,497 Mark II - While(results.next()) {}
• 5/49 Mark III - close connections

the code:

// GET SCENARIO LIST
function getScenarioQuickList() {

  var start = new Date().getTime();

  var conn = Jdbc.getCloudSqlConnection('jdbc:google:mysql://...', user, userPwd);

  var query = 'SELECT a.`lvl`, a.`pubShort`, a.`scenTitle`, a.`pdfLink`';
    query += 'FROM `SA` a WHERE a.`scenId` <> "ZZZ99998" AND a.`scenId` <> "ZZZ99999" ORDER BY a.`scenId`;';
      
  var stmt = conn.prepareStatement(query);
  
  var results = stmt.executeQuery();
  
  var scenList = [];

  console.log(new Date().getTime()-start);  // mark 1
  
  // Push results to array

  start = new Date().getTime();

  while (results.next()) {
    scenList.push({
      'lvl': results.getString(1),
      'pubShort': results.getString(2),
      'scenTitle': results.getString(3),
      'pdfLink': results.getString(4),
    }); // close push
  } // close while
  
  console.log(new Date().getTime()-start); // mark 2

  start = new Date().getTime();

  results.close();
  stmt.close();
  conn.close();
  
  console.log(new Date().getTime()-start); // mark 3

  return scenList;

}