**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.
This medium-level General/Other question appears frequently in data engineering interviews at companies like Citi. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (partition, spark) will help you answer variations of this question confidently.
Break this problem into components. Identify the core trade-offs involved, then walk the interviewer through your reasoning step by step. Demonstrate awareness of edge cases and production considerations - this is what separates good answers from great ones.
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.
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Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked General/Other interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.