1. A computer-implemented method comprising: receiving, from a user, a query that specifies a search criterion and a post-processing function prototype; generating, from the query, a topology definition that specifies: one or more source nodes and at least one processing node, wherein the processing node is specified in the topology to receive, from the one or more source nodes, one or more streams of data object identifiers of data objects that satisfy the search criterion, and wherein the processing node is specified in the topology to output a stream of data objects corresponding to the data object identifiers; and a post-processing node according to the post-processing function prototype, wherein the post-processing node is specified in the topology to receive a stream of data objects output by the processing node, perform one or more operations on the data objects according to the post-processing function prototype, and is specified in the topology to output one or more modified data objects; and providing the topology definition to a real-time stream computing system for execution.