I think this is one of the few benefits of micro service architectures. You end up with much smaller pieces to migrate over. And if the service is well define

I think this is one of the few benefits of micro service architectures. You end up with much smaller pieces to migrate over. And if the service is well defined and you have ample logging for endpoints you actually could re-write it. Mind you; you usually end up with the services all in different states of node/jdk/etc versioning(at least the companies I worked at).