A data processing system configured to store a plurality of data entities in volatile memories of multiple different computing devices. The data processing system comprises a first computing device having a first volatile memory configured to store a first data entity; and a second computing device having a second volatile memory configured to store a copy of the first data entity. The first computing device is configured to perform: receiving an indication to update the first data entity; after receiving the indication, updating the first data entity in the first volatile memory, and providing to the second computing device an indication to update the copy of the first data entity; and providing an indication that the first data entity has been updated, after receiving information from the second computing device indicating that the copy of the first data entity has been updated in the second volatile memory.