Monitor logs and Grafana boards after deploying the MultiBackendSessionStore code to all wikis.
[ ] 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
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.