Monitor logs and Grafana boards after deploying the MultiBackendSessionStore code to all wikis for one week to ensure stability and no errors.
[ ] Logstash: https://logstash.wikimedia.org/goto/573b48796434c92785584026f0baca10 (sessions dashboard)
[ ] Cassandra (session store) Grafana dashboard: https://grafana.wikimedia.org/d/000001590/sessionstore
[ ] BagOStuff by keygroup (`MWSession`): https://grafana.wikimedia.org/d/4plhqSPGk/bagostuff-stats-by-key-group
[ ] MediaWiki/CentralAuth sessions: https://grafana.wikimedia.org/d/fd0c8c5e-3b26-4a90-bca2-a2504de1badc/mediawiki-and-centralauth-sessions?orgId=1&from=now-24h&to=now&timezone=utc&var-kWiki=$__all&editIndex=0
[ ] Remove/Hide the single backend session store panel from the dashboard since it's no longer used.
If everything looks good by the end of this week, this can be resolved. This can be done simultaneously with {T402850} as we prepare to do a proper switch to a dedicated backend for anonymous sessions.