receiving, by one or more execution nodes, a query plan to execute a query referencing plurality of databases stored in a network-based data system, the query plan including a connection string based on compiled objects in the plurality of databases referenced in the query, the connection string including mapping information related to the plurality of databases and cluster information describing locations of the plurality of databases are stored in the network-based data system;

retrieving read versions of the objects from the plurality of databases using the connection string information in the query plan;

retrieving transaction status information for the objects;

generating transaction contexts for the objects based on the transaction status information; and

performing a scan operator of a set of operators in the query plan on at least one of the objects using the respective transaction context of the object.