[pas]

Could you share your thoughts on how likely and how soon will the RocksDB engine be available as part of normal Cassandra? Also, how big is the gap between 3.0.x and 3.x? Any improvements between 3.0.x and 3.x regarding tail latency/performance? Thanks!

[jjirsa]

I think it's likely. It's decidedly nontrivial, and the hardest part will be the (very slow) design phase where we actually make sure the interfaces are defined properly, but I think there are enough interested people to make sure it happens.

There are some meaningful changes between 3.0 and 3.11 (notably a compressed chunk cache for storing some intermediate data blocks and a significant change to the way the column index is deserialized) that do help tail latencies, and there's certainly quite a bit more low hanging fruit, but the biggest contributor to p99 latencies is the GC collections, and the read path still contributes the most JVM garbage, so this is still probably a meaningful improvement over 3.11.