Yes, SQL Server will work fine: data access to SQL Server is handled entirely in the Write-Behind event callback that is defined in
your code, so the ScaleOut service is not directly involved in database communication--it's handled entirely by your application, allowing you to use whatever database you need.
More information can be found in these links:
The front-end clients that access the ScaleOut service can be configured to auto scale, but the ScaleOut service itself does not yet support auto scaling. It's on our roadmap (some preliminary work has been done), but I don't have a date for it yet. If you'd like to discuss your timeline and requirements offline then go ahead and contact us through
this form and we can set up a time.