Disclosed are various embodiments for scalable workflow processing. In one embodiment, a plurality of decision applications each embody a functional expression of a corresponding one of a plurality of workflow definitions. Each of the plurality of decision applications is configured to be repeatedly instantiated. A workflow execution application is configured to orchestrate an execution of each one of a plurality of workflow instances. The workflow execution application is in data communication with each instance of a respective one of the plurality of decision applications. Each of the plurality of decision applications is configured to determine a next action to be taken for respective ones of the plurality of workflow instances.