A data representation that represents source data at a data source can be maintained. A request to perform an edit can be received from a client, and a request to make the edit to the source data can be sent to the data source. The edit can be optimistically applied to the data representation. Additionally, a change notification can be sent to the client. The change notification can indicate one or more changes to the data representation, where the change(s) resulted from the application of the edit to the data representation. A notification can be received from the data source after applying the edit to the data representation and after sending the change notification. The notification from the data source can indicate whether the edit to the source data succeeded.