Yes, here's a paper on scalability that should be helpful http://www.dreamfactory.com/publications/DreamFactory_Scalability_V4.pdf.
You can use an external database for user and roles.
Connecting to another Database Server after initial setup
To connect to a different Database Server after initial setup...
Edit the .env file at the installation root and change the following configuration.
DB_DRIVER=mysql ## Supported drivers are sqlite (default), mysql, pgsql
DB_HOST=localhost
DB_DATABASE=dreamfactory
DB_USERNAME=username
DB_PASSWORD=secret
DB_PORT=3306
Run following command to clear system cache.
php artisan cache:clear
Run DreamFactory setup wizard.
php artisan dreamfactory:setup
Make sure your web server can read/write from/to storage/ (sub directories) and bootstrap/cache/ directories.
Example:
sudo chown -R {www user}:{your user group} storage/ bootstrap/cache/
sudo chmod -R 2775 storage/ bootstrap/cache/
Configure your web server to serve the public/ directory and launch your instance from a browser.
Note: The default composer.json has the more common package additions listed. To see all available packages, see the composer.json-all-dist. Likewise to see the minimum required packages, see the composer.json-min-dist.