Techniques are described for efficient query processing and data change propagation to a secondary database system. The secondary database system may execute queries received at a primary database system. Database changes made at the primary system are copied to the secondary system. The primary system receives a query to be executed on either the primary system or the secondary system. The primary system determines whether to send the query to the secondary system based upon whether data objects stored within the secondary system have pending changes that need to be applied to the data objects. The pending changes are stored within in-memory journals within the primary system. The primary system scans for the pending changes to the data objects and sends the pending changes to the secondary system. The secondary system then receives and applies the pending changes to the data objects within the secondary system. Upon applying the pending changes, the secondary system executes the query.