Samba offers the greatest flexibility in backend account database design of any SMB/CIFS server technology available today. The flexibility is immediately obvious as one begins to explore this capability.

It is possible to specify not only multiple password backends, but even multiple backends of the same type. For example, to use two different tdbsam databases:

What is possible is not always sensible. Be careful to avoid complexity to the point that it may be said that the solution is “too clever by half!”