Abstract. Since the emerge of Salesforce.com, more and more business applications tend to move towards Software as a Service. In order to target Small and Medium-sized Enterprises, platform providers need to lower their operational costs and establish an ecosystem of partners, customizing their generic solution, to push their products into spot markets. This paper categorizes customization options, identifies cornerstones of a customizable, multi-tenancy aware infrastructure, proposes a framework that encapsulates multi-tenancy, and introduces a technique for partner back-end customizations with regard to a given real-world scenario.