Magento – Is it possible to have two stores sharing one backend and the same inventory

Assuming you have 1 domain: domain.com with a running Magento installation with 2 websites (with each 1 store) I would suggest the solution below.

Create 2 sub-directories in your Magento root folder like this:

<magento-root-folder>
  en
    symlink to ../app
    symlink to ../errors
    symlink to ../.htaccess
    symlink to ../js
    symlink to ../lib
    symlink to ../media
    symlink to ../skin
    copy of ../index.php with some modifications
  de
    symlink to ../app
    symlink to ../errors
    symlink to ../.htaccess
    symlink to ../js
    symlink to ../lib
    symlink to ../media
    symlink to ../skin
    copy of index.php with some modifications

After that I would adjust the base urls of both websites to be:

domain.com/en
domain.com/de

Make the requirement modifications of index.php in each sub-directory:

Replace

/* Store or website code */
$mageRunCode = isset($_SERVER['MAGE_RUN_CODE']) ? $_SERVER['MAGE_RUN_CODE'] : '';

/* Run store or run website */
$mageRunType = isset($_SERVER['MAGE_RUN_TYPE']) ? $_SERVER['MAGE_RUN_TYPE'] : 'store';

Mage::run($mageRunCode, $mageRunType);

with (*don't forget to modify 'THE_CORRECT_STORE_CODE' in the below code snippet*)

Mage::run('THE_CORRECT_STORE_CODE', 'store');

Inside your Magento-root folder I would create a index.html file that will server as the language selection page. (When doing this don't forget to change the DirectoryIndex index.php inside the .htaccess file)

Also in this .htaccess file you should redirect all traffic that wants to visit non language/country specific urls to the language selection page...

I hope this helps you out ;)

A neat solution is to use an Inventory Management system that will act as a server, keeping your stock in sync across the different Magento installations.

Megaventory is a Magento compatible ERP which adds inventory management in multiple locations, ordering and reporting capabilities to your ecommerce store. It also features a powerful manufacturing module that ties well with Magento's bundle products.

If you use this solution, you will be handling all your ordering and your warehouse through Megaventory which will serve all the product details and the stock levels to your different e-commerce sites.

Also, since we plan to add integrations with more ecommerce platforms and other services so you can start building a powerful modular system to automate your business operations and data analysis.