Methods and systems are provided, for persistent querying in a federated database system. A federated database system has a plurality of connectable database management system nodes, each database node having at least one database. Persistent querying includes: receiving a query at a first database node and propagating the query from the first database node to other database nodes in the federated database system. A responding database node satisfying the query: obtains a query results set; defines a topic identifier for the query; and publishes subsequent messages relating to the topic identifier when data updates are available. The first database node receives query results sets from one or more responding nodes and the first database node subscribes to topic identifiers for publications of subsequent messages from the responding database nodes. Subsequent messages are published relating to the query along the connection through which the query is returned.