Major Description
RocksDbWindowStore currently does not use caches, but its window segments implemented as RocksDbStore does. However, its range query fetch(key, fromTime, toTime) will cause all its touched segments' cache to be flushed.
After KAFKA-3777, we should change its implementation for KStreamWindowAggregation / KStreamWindowReduce to not use fetch, but just as multiple get calls on the underlying segments, one for each affected window range.