Disclaimer: This is listed as $100, but it's free for premium members of our website (which costs $25).[/B]
This gives master/slave database support to XenForo without needing to edit any standard XenForo files (other than adding your slave DB servers to your config.php file).
The "$25 cost" is actually the maximum cost for 1 month of premium membership on our site. If you are already a premium member, it's free (as are support and upgrades).
This is the database adapter we are using on https://forums.digitalpoint.com