Ah, thanks. The first link seems something specific to Shrine. The bottomline is...

		throwaway7783 11 months ago \| parent \| context \| favorite \| on: Making Postgres scale Ah, thanks. The first link seems something specific to Shrine. The bottomline is concurrent updates to different parts of JSONB need row level locking for correct behavior in Postgresql. This is not an important issue for us. Thank you for the pointers

You can trivially do it without locking using a version column.