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Explain read and write modes in Spark.

Spark/Big Datahard0.5 min readPremium

**Why it matters**: At scale, design choices directly impact reliability, latency, and cost. Wrong decisions compound across jobs and teams. Spark read modes: spark.read loads data (default overwrites for file sources). Write modes: (1) overwrite—replaces target; (2)...

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Frequency
Low
Asked at 1 company
Category
452
questions in Spark/Big Data
Difficulty Split
88E|81M|283H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Globant
Key Concepts Tested
optimizationpartitionspark

Why This Question Matters

This hard-level Spark/Big Data question appears frequently in data engineering interviews at companies like Globant. 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.

How to Approach This

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.

Expert Answer
97 words

Why it matters: At scale, design choices directly impact reliability, latency, and cost. Wrong decisions compound across jobs and teams.

Spark read modes: spark.read loads data (default overwrites for file sources). Write modes: (1) overwrite—replaces target; (2) append—adds data; (3) ignore—no-op if exists; (4) errorIfExists—fail if exists. Example: df.write.mode('append').parquet(path). For Delta: overwriteSchema; replaceWhere for conditional overwrite. Best practices: use dynamic partition overwrite for partitioned tables; use Delta merge for upserts; validate schema on read when using append.

Scalability trade-offs: Partition/parallelism limits; single points of failure; horizontal vs vertical scaling. Cost implications: Sizing, spot vs reserved, optimization ROI.

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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 a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.

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