If you store the session in a cookie you probably want to use the JsonSerializer for both apps: Rails.application.config.action_dispatch.cookies_serializer = :json
Yes, the applications are connected to the same database.
The Rails 4.1 application is using the cookie session store so I don’t need to consult the database.
I need the Rails 6 application to read/write compatible session cookies until such a time as I can move everything over into that and move to a different session store.