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Join two petabyte fact tables where both are skewed on the same key. Neither fits in memory. Make it finish.

Basic salting assumes one side is a small dimension you can explode. When both sides are huge and skewed, exploding either one blows up the cluster. The staff move is to split hot keys out and handle them on a different plan entirely.

Updated Aug 2026 · Grounded in real Forward Deployed Engineer interview loops and written to a senior-engineer editorial bar.

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