A received graph-based program specification includes: a plurality of components, each corresponding to at least one operation; and a plurality of directed links each connecting an upstream component to a downstream component. Processed code is generated representing one or more groups of operations by: identifying a possible level of concurrency in a first group of operations based at least in part on a topology of the graph, such that multiple operations in the first group are not prevented by the topology of the graph from executing concurrently; analyzing at least some of the operations in the first group to determine runtime characteristics associated with the analyzed operations; and generating processed code for executing the operations, where the processed code enforces a reduced level of concurrency in the first group, lower than the identified possible level of concurrency, based at least in part on the determined runtime characteristics.