Roman Komkov presented on Cassandra at Glogster. Glogster EDU is an online platform used by 19 million users for presentation and learning, generating over 45,000 new projects daily. Glogster has used Cassandra since 2011 as its primary database, starting with 0.6-0.8 and upgrading over time. Currently it uses a 5 node cluster storing 600GB of data. Upgrades brought challenges around migration, repairs, and a data loss incident that took 10 days to repair after decommissioning an old datacenter without proper hints handling. Lessons included increasing repair windows, enabling parallel repairs, and regularly scheduling backups and repairs.