[majidazimi]

Well, other than storage engine, the next big part of a database software is the query planner/optimizer which Cassandra doesn't have (due to simple KV nature of it). So there isn't much remaining. In a long term plan, rewrite them all and you have single code base and you'll benefit from mighty C++ in other components of the database. And there is still room for more optimizations: SIMD, ...

The GC problem is not limited to C*. This shit(virtual machine) is hitting the whole Hadoop stack: HDFS, Hive, Spark, Flink, Pig...

Immense number of tickets in any fairly large cluster is related somewhat to GC and JVM behavior.