Shuffle Service Architecture

Concepts: paShuffleOptimization

What They Want to Hear 'By default, shuffle data is stored on the executor that produced it. If that executor dies, all downstream stages that need its shuffle data must re-compute. The external shuffle service decouples shuffle storage from executors: shuffle files live on the node's local disk and survive executor restarts. This is critical for dynamic allocation, where executors are added and removed frequently. Without it, removing an idle executor destroys its shuffle data and causes expensive re-computation.' This is the answer that shows you understand the interaction between shuffle, fault tolerance, and dynamic allocation.