Why More Executors Stopped Helping: Skew, Memory, Files, and the Cost Curve
Doubling the cluster rarely halves the runtime. What actually sets the limit is the slowest task — and the fixes for it are usually not more machines.
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Spill
Spilling is not an error; it is the engine refusing to crash. It also turns the fast part of a query into the slow part, which is why it shows up in metrics.
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Do You Actually Need a Cluster? When Distributed Processing Pays and When It Costs
A cluster is not a size upgrade; it is a different set of costs. What actually forces distribution, and what a single node handles that people assume it cannot.