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This KIP adds the cache.max.bytes.buffering configuration to the streams configuration as described above. 

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Proposed implementation outline

1. Change the RocksDB implementation for KStream windowed aggregations, to not use “range queries” but multiple gets, so that we can leverage caches for it as well.

2. Extract the LRU cache out of RocksDBStore, as a separate store for KGroupedStream.aggregate() / reduce(), and KStream.aggregateByKey() / reduceByKey().

3. Add the LRU cache for KTable.to() operator.

4. Add the above config into StreamsConfig

    

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