Is there a way to pass a variable by value to another flow service to prevent the modifications performed in the flow service from being returned to the calling services?

Calling the service via transformer may do the trick.

You might try copying the variable that you want to leave untouched to another var and pass the temp var. This will work just dandy for strings as mapping string vars makes a copy. However this won’t work for records unless you do a deep copy/clone.

For the this particular instance I am dealing with records and record lists. I applied the same concept that you mentioned; with the caveat that you must map at the lowest common denominator from the source record to the destination record, which is effectively implementing the deep copy, and then you must drop the source record. Not sure about the performance in this instance, but it was much faster implementation than implementing Clone in a java service.