Why it matters

Stateful streaming enables aggregations + joins over time. Understanding shapes real streaming.

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The architecture

State store: RocksDB (default in Spark 3.2+) or HDFS.

Checkpoint: durable recovery point.

Stateful streaming stackStateful opaggregate, dedupe, windowState storeRocksDB / HDFSCheckpointfor recoveryRocksDB state store more scalable for large state
State handling.
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How it works end to end

State store: RocksDB for scale, HDFS legacy.

Checkpointing: at trigger interval.

State size: monitor + bound.

Recovery: checkpoint + state restore.