Github user aljoscha commented on the issue: https://github.com/apache/flink/pull/5185 Thanks for the update. Regarding migration, I think the format that we write to the savepoint must be the same between the two `ListState` implementations. @StefanRRichter could you please have a look at this? And also @StephanEwen, I think you did a similar PoC implementation of this a while back. @je-ik It would make sense to change the title of the PR to reflect what this does now better.