Reviewed by Aditya Kumar · Last reviewed 2026-03-24
**STAR approach**: **Situation**: Job ran 2 hr, now 6 hr. **Task**: Find root cause. **Analysis**: (1) Data volume growth—compare input size. (2) Skew—Spark UI shows uneven partitions. (3) Resource contention—other jobs. (4) Source throttling—DB or API limits. (5) Partition...
Pro-Move: 'We had a job slow 3×—Spark UI showed 1 partition at 2hr; added salting, back to 30min.' Red Flag: Restarting or adding resources without diagnosing—mask the problem.
STAR approach: Situation: Job ran 2 hr, now 6 hr. Task: Find root cause. Analysis: (1) Data volume growth—compare input size. (2) Skew—Spark UI shows uneven partitions. (3) Resource contention—other jobs. (4) Source throttling—DB or API limits. (5) Partition pruning—missing partitions? Actions: Add partitions; salting for skew; increase resources; fix source limits. Result: Document in runbook; add monitoring. Best practice: Compare metrics (input GB, partition count); use Spark UI for skew.
Pro-Move: 'We had a job slow 3×—Spark UI showed 1 partition at 2hr; added salting, back to 30min.' Red Flag: Restarting or adding resources without diagnosing—mask the problem.
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