An operation is performed for executing a plurality of first-level queries. Execution of each first level query determines if a respective type of operational condition exists within a network. If needed due to the quantity of first-level queries, the first-level queries are executed in a sampled manner such that less than all of the first-level queries are applied to a specified collection of network elements of the network during each one of a plurality of instances of executing the first-level queries being performed and such that all of the first-level queries are applied to the specified collection of network elements in accordance with a prescribed query execution timeframe. An operation is performed for executing a second-level query in response to one of the first-level queries determining that the respective type of operational condition exists within the network. Executing the second-level query results in determination of diagnostic information specific to the determined type of operational condition.