Delete rows based on values within cell, optimising

I have script running on a weekly bases deleting rows from a document and then pasting these values to another sheet for data analysis, however as the document grows (+20,0000 rows) my script times out. Anyway on how to optimise the script to perhaps use less processing/memory and run faster?

var rowsDeleted = 0;
for (var i = 0; i <= numRows - 1; i++) {
var row = values[i];
if (row[0] == 'delete' || row[0] == '') {
data.deleteRow((parseInt(i)+1) - rowsDeleted);
rowsDeleted++;
}
}

In your situation, I understand as follows.

• There are a lot of rows which are deleted.
• The rows are not continued. So the rows have to be deleted row by row using deleteRow().

If my understanding is correct, how about this modification?

Modification points :

• Use batchUpdate of Sheets API.
  • By using Sheets API, the discrete rows can be deleted by one API call.
• Create the list of rows which are deleted as the request body for Sheets API.
• Delete the rows by batchUpdate of Sheets API with the request body.

In order to use Sheets API, please enable Sheets API at Advanced Google Services and API console. About the how to enable them, please check here.

Modified script :

var spreadsheetId = "#####"; // Please input spreadsheet ID.
var sheetId = "#####"; // Please input sheet ID.

var deleteRows = [];
for (var i = values.length - 1; i >= 0; i--) {
  if (values[i] == "delete" || values[i] == "") {
    deleteRows.push({
      "deleteRange": {
        "shiftDimension": "ROWS",
        "range": {
          "startRowIndex": i,
          "endRowIndex": i + 1,
          "sheetId": sheetId
        }
      }
    });
  }
}
Sheets.Spreadsheets.batchUpdate({"requests": deleteRows}, spreadsheetId);

Note :

• In this modified script, it supposes that the retrieved values from Spreadsheet is in values.
• Before you run this, please input spreadsheet ID and sheet ID having the rows you want to delete.

If this was not result what you want, I'm sorry.