The driver supports both promises and callbacks for the asynchronous methods exposed in the Client and Metadata prototypes, you can choose the approach that suits your needs.

client.execute('SELECT name, email FROM users')
  .then(result => console.log('User with email %s', result.rows[0].email));

When a callback is not provided as the last argument, the driver will return a Promise, without the need to promisify the driver module. Returned promises are instances of Promise global object and are created using the default constructor: new Promise(executor).

In case you want the driver to use a third party Promise module (ie: bluebird) to create the Promise instances, you can optionally provide your own factory method when creating the Client instance, for example:

const BbPromise = require('bluebird');
const client = new Client({
  contactPoints,
  localDataCenter,
  promiseFactory: BbPromise.fromCallback
});

All asynchronous methods of the driver supports an optional callback as the last argument.

client.execute('SELECT name, email FROM users', function(err, result) {
  assert.ifError(err);
  console.log('User with email %s', result.rows[0].email);
});