A computer-implemented method for supporting client-specific extensions within a multi-tenant platform comprising: receiving, from a client device operated by a client, the client being a tenant of the multi-tenant platform, and using an application programming interface exposed by the framework, a request for access to an instance of an object model, the instance being stored in a data persistency, wherein the framework uses metadata of the object model describing the structure and attributes of the instance thereof and being provided by a metadata repository to access data of the instance stored in the data persistency; identifying, in a metadata persistency being a database table of the metadata repository, extension metadata stored in a row of the metadata persistency which is associated with the object model and with the client identifying, in the metadata persistency being a database table of the metadata repository, client-independent metadata of the object model stored in a row of the metadata persistency; merging the client-independent metadata and the extension metadata associated with the client to create a merged object model by overlaying the identified extension metadata upon the identified client-independent metadata to replace portions of the client-independent metadata with corresponding portions of the extension metadata where the portions differ and to add portions of the extension metadata for which no corresponding client-independent metadata exists; and accessing the instance of the object model from the data persistency based on the corresponding merged object model for the instance, wherein for each row in the metadata persistency a client value "000" indicates client-independent metadata and a client value other than "000" indicates extension metadata associated to the client specified by the client value, so that the extension metadata of the client is separated from extension metadata of another client and from the client-independent metadata in the metadata persistency. receiving, from a client device operated by a client, the client being a tenant of the multi-tenant platform, and using an application programming interface exposed by the framework, a request for access to an instance of an object model, the instance being stored in a data persistency, wherein the framework uses metadata of the object model describing the structure and attributes of the instance thereof and being provided by a metadata repository to access data of the instance stored in the data persistency; identifying, in a metadata persistency being a database table of the metadata repository, extension metadata stored in a row of the metadata persistency which is associated with the object model and with the client identifying, in the metadata persistency being a database table of the metadata repository, client-independent metadata of the object model stored in a row of the metadata persistency; merging the client-independent metadata and the extension metadata associated with the client to create a merged object model by overlaying the identified extension metadata upon the identified client-independent metadata to replace portions of the client-independent metadata with corresponding portions of the extension metadata where the portions differ and to add portions of the extension metadata for which no corresponding client-independent metadata exists; and accessing the instance of the object model from the data persistency based on the corresponding merged object model for the instance, wherein for each row in the metadata persistency a client value "000" indicates client-independent metadata and a client value other than "000" indicates extension metadata associated to the client specified by the client value, so that the extension metadata of the client is separated from extension metadata of another client and from the client-independent metadata in the metadata persistency.