Unified Compaction Strategy consolidates compaction strategies

Cassandra 5.0 introduces Unified Compaction Strategy (UCS, CEP-26), a new compaction strategy designed to unify and improve upon existing strategies (STCS, LCS, TWCS). This changes compaction behavior and may require configuration migration.

Evaluate UCS for tables currently using STCS, LCS, or TWCS. Monitor cassandra_compaction_tasks_pending, cassandra_compaction_tasks_completed, and cassandra_compaction_size_compacted for compaction throughput. Track cassandra_live_ss_table count and cassandra_sstable_live_disk_space_used for storage efficiency. Review UCS configuration parameters in CEP-26 and migrate compaction strategy settings.