Computer-implemented methods for synchronizing data between a server and a client are provided. In one aspect, a method includes receiving a request from a client to synchronize data. The request includes a synchronization token that includes client recent synchronization signatures, each client recent synchronization signature representing a state of data synchronization on the client for a certain time period. The method also includes comparing each client recent synchronization signature with a corresponding server recent synchronization signature representing data on a server for the same time period. When the comparison indicates that the data on the client for the time period represented by the client recent synchronization signature is not synchronized with corresponding data on the server for the time period, then the method includes sending the data on the server for the time period to the client. Systems and machine-readable media are also provided.