Some information on performance when using the DataStore back end in Database abstraction with google apps script
The library reference is 

Mj61W-201_t_zC9fJg1IzYiz3TLx7pV4j  

Comparing scriptDB, parse and datastore

In Migrate data from scriptDb to Datastore I showed how to copy over data easily from scriptdb to datastore. The good thing about abstracting the database is that code is the same regardless of which database use you are using (once you’ve got the handle). 
In this example I’m copying 1000 records from scriptDB to each of parse.com, datastore and parse.com. Note that each of these drivers using batching, so it’s a fair enough comparison. For the purposes of the test, I’ve switched caching off in all cases. There are 3 operations performed – deleting 1000 records, adding 1000 records and querying them.
Note: since doing this test, I’ve improved batching on parse.com deletion – see Comparing all back ends performance for the improved parse.com performance numbers.

Here’s the code

function scriptDBCopyToDataStore (accessToken) {

  //get some data from - no Siloid in original data
  var handler = new cDataHandler.DataHandler (
      '',                        
      cDataHandler.dhConstants.DB.SCRIPTDB,      
      undefined,
      'myddb',
      ScriptDb.getMyDb(), 
      undefined,                       
      false,             
      'bruce',
      undefined,
      true);
  assert(handler.isHappy(), 'unable to get scriptdb handler','handler');

   // get a datastore handler
   var dsHandler = new cDataHandler.DataHandler (
     'customers',                              // Kind
     cDataHandler.dhConstants.DB.DATASTORE,    // Datastore
     undefined, 
     'xliberationdatastoredev',                   // project id
     undefined, 
     undefined,
     false,                                     // analytics opt out
     'bruce',                                  // analytics debugging tracking 
     accessToken,                              // the access token
     true);                                    // disable caching for testing  
  assert(dsHandler.isHappy(), 'unable to get scriptdb handler','handler');

  var userStore = PropertiesService.getScriptProperties();
    
   // get a parse handler
   var parseHandler = new cDataHandler.DataHandler (
     'customers',                              // Kind
     cDataHandler.dhConstants.DB.PARSE,    
     undefined, 
     'parsecustomers',                   
     JSON.parse(userStore.getProperty("parseKeys")), 
     undefined,
     false,                                     // analytics opt out
     'bruce',                                  // analytics debugging tracking 
     accessToken,                              // the access token
     true);                                    // disable caching for testing  
  
  // get the source data
  var data = handler.query();
  assert (data.handleCode >=0, data, 'getting data from script');
  
  // copy it to datastore
  deleteAndCopy (dsHandler, data.data);
  
  // copy it to parse.com
  deleteAndCopy (parseHandler, data.data);
  
  // copy it to scriptDB
  deleteAndCopy (handler, data.data);

  // delete whats there, insert and query - can be shared across handlers
  function deleteAndCopy (theHandler,theData) {

  // delete everything in current db
    var result = theHandler.remove();
    assert (result.handleCode >=0, result, 'deleting data from ' + theHandler.getDBName() );
 
  // copy it to db  
    var result = theHandler.save(theData);
    assert (result.handleCode >=0, result, 'writing data to ' +  theHandler.getDBName());

  // read it back and make sure it all made it
    var result = theHandler.query();
    assert (result.handleCode >=0, result, 'querying data from ' +  theHandler.getDBName() );

    Logger.log(result.data.length +' objects in ' + theHandler.getDBName());
  }
}

 

Summary

Although DataStore is quicker at deletion, using its JSON API makes it slower than Parse for both querying and writing. Unless you are planning to use DataStore for its extensive capabilities and scalability outside the simple scope of being a replacement for ScriptDB, it’s hard to see why you wouldn’t choose parse.com and avoid all those quota problems

See more like this in Database abstraction with google apps script and Datastore driver and for all back end performance see Comparing all back ends performance