I recommend rethinking about this design, hard to maintain, slow startup and repair . About GC, try to replace CMS with G1 , see doc : https://docs.datastax.com/en/dse/6.0/dse-admin/datastax_enterprise/operations/opsTuningGcAbout.html BTW, also many columns may affect performance, see doc: https://thelastpickle.com/blog/2020/12/17/impacts-of-many-columns-in-cassandra-table.html
Cheers, Yakir Gibraltar
