does FlowActionsService webservice support callback?

Summary

looking for callback functionality on middleware after invoking payrollflow

Content

does cloud HCM FlowActionsService webservice support callback functionality when a payroll flow is invoked from a middleware? polling status of the payroll flow until the process is complete is not an option we are looking at as it could keep middleware flow waiting. This is not desirable for long running processes.

appreciate any inputs.