is RosckDB backend available in 3.0 preview?

[kant kodali]

Hi All,

1. is RosckDB backend available in 3.0 preview?
2. if RocksDB can store intermediate results of a stream-stream join can I
run  streaming join queries forever? forever I mean until I run out of
disk. or put it another can I run the stream-stream join queries for years
if necessary (imagine I got lot of disk capacity but not a whole lot of
RAM)?
3. Does is to do incremental checkpointing to HDFS?

Thanks!