Github user pnowojski commented on the issue:
https://github.com/apache/flink/pull/4722
We have got carried away with those concurrent modifications and snapshots.
To rewrite keyed state variable from an old to a new one, old is used as a read
only. Thus `getKeys` for the the old one doesn't have to care about any
modifications.
I have reverted snapshot rocks db changes.---
