The default compaction strategy for system.paxos table is LCS for performance reason:
CASSANDRA-7753. But for CAS heavily used cluster, the system is busy with system.paxos compaction.
As the data in paxos table are TTL'ed, TWCS might be a better fit. In our test, it significantly reduced the number of compaction without impacting the latency too much:
The time window for TWCS is set to 2 minutes for the test.
Here is the p99 latency impact:
the yellow one is LCS, the purple one is TWCS. Average p99 has about 10% increase.