Reviewed by Aditya Kumar · Last reviewed 2026-03-25
**Why it matters**: At scale, design choices directly impact reliability, latency, and cost. Wrong decisions compound across jobs and teams. Stream data to Delta Lake with `spark.readStream.format('delta')` and write using...
This hard-level Spark/Big Data question appears frequently in data engineering interviews at companies like Meesho. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (optimization, partition, spark) will help you answer variations of this question confidently.
This is a senior-level question that tests architectural thinking. Lead with the high-level design, then drill into specifics. Discuss trade-offs explicitly - there is rarely one correct answer. Show awareness of scale, fault tolerance, and operational complexity.
Why it matters: At scale, design choices directly impact reliability, latency, and cost. Wrong decisions compound across jobs and teams.
Stream data to Delta Lake with spark.readStream.format('delta') and write using .writeStream.format('delta').option('checkpointLocation', path).start(). Schema evolution: Enable with option('mergeSchema', 'true') or option('overwriteSchema', 'true'). For additive columns, use mergeSchema; new columns get null for old records. For breaking changes, use ALTER TABLE ADD COLUMN in Delta. Best practices: Define schema explicitly when possible; use schema.evolution.mode; run OPTIMIZE and Z-ORDER periodically; set checkpointLocation for exactly-once semantics.
Scalability trade-offs: Partition/parallelism limits; single points of failure; horizontal vs vertical scaling. Cost implications: Sizing, spot vs reserved, optimization ROI.
Red Flag: mergeSchema without validation. Pro-Move: 'Schema registry; additive-only; test in dev.'
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According to DataEngPrep.tech, this is one of the most frequently asked Spark/Big Data interview questions, reported at 1 company. DataEngPrep.tech maintains an editor-reviewed database of 1,863 data engineering interview questions across 7 categories.