Transactions within a process model are determined by grouping a set of individual process activities into a single transaction. This effectively reduces the processing overhead, and, therefore, improves the overall throughput and latency of the execution of the process model. The transaction is determined by performing an optimization procedure that takes into account the structure of the process model as well as various properties of the single process activities of the process model. Analysis of the properties of the process activities as well as application of the optimization procedure is performed dynamically during execution of the process model by a workflow engine.