Compaction Strategy Mismatch Degrading Node Density
warningUsing STCS (Size-Tiered) creates unbounded SSTable growth and prevents fast streaming, while LCS (Leveled) causes excessive write amplification under heavy load. Both reduce effective node density and operational efficiency compared to UCS (Unified) in Cassandra 5.0+.
Monitor cassandra_compaction_size_compacted and cassandra_live_ss_table metrics. STCS shows very large SSTables (multi-GB) with infrequent compaction. LCS shows constant high compaction overhead with cassandra_compaction_tasks_pending rarely reaching zero despite adequate throughput settings.
For Cassandra 5.0+, migrate to UnifiedCompactionStrategy (UCS) using ALTER TABLE with 'scaling_parameters': 'T4' (STCS-like) or 'L10' (LCS-like). For older versions on write-heavy workloads, prefer STCS; for read-heavy with strict latency SLOs, use LCS. Monitor SSTable count per read (nodetool tablehistograms) post-migration to confirm improvement.