The present invention discloses a new synchronization architecture for synchronization of data between different clients by using a central synchronization server linked to a Back End data store which additionally provides a cache for permanently buffering incoming updates into a permanent store by assigning an unique cache identifier (ID). Write conflicts between the synchronization server writing new entries to the cache and updates replicated from backend to cache are solved using a blocking mechanism based on the cache IDs, so that the backend updates are blocked as long as incoming updates from the clients having the same cache ID are not completely written into the cache during a synchronization session. The present invention is preferably suited for a synchronization architecture having a high number of clients connected with the central synchronization server as blocking of the Back End data store, and the connection and the transport to the Back End data store are minimized.