Orchestration of a sequence of computations by external systems

A method is provided for orchestrating a workflow. In some embodiments, the method includes executing a workflow including a first controller that includes a first callout function and a first callback function and corresponds to a first microservice. Execution of the workflow includes execution of the first callout function that causes invocation of the first call to the first microservice. The method further includes receiving a notification of an execution state from the first microservice and transmitting the execution state to the first callback function. The method also includes in response to transmitting the execution state to the first callback function, receiving a function output based on the execution state from the first callback function. The method further includes determining, based on the function output, whether to execute a subsequent controller. The method also includes in response to a determination to execute the subsequent controller, executing the subsequent controller.