I think the difference here is that the migration of internal state happens the moment the module is swapped out in memory. Erlang doesn't have mutable state, so state is instead passed around within a module. When a fix needs to be deployed, the two versions (old and new) run simultaneously, any new processes immediately run the new code, old processes call a `code_change` function which takes the current state within that process, performs any transformations required for the new code, and then the old module code is swapped out for the new.
That's not at all a perfect explanation of the process, but it's more or less useful enough to describe the difference between the two platforms.
That's not at all a perfect explanation of the process, but it's more or less useful enough to describe the difference between the two platforms.