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What are the advantages of using Delta Lake over Parquet?

Spark/Big Dataeasy0.5 min readPremium

**Why Delta Over Raw Parquet**: Parquet is immutable; no deletes, no transactional writes. Concurrent writers create corrupt state. Delta adds transaction log and metadata. **Delta Advantages**: (1) **ACID**—concurrent writes; readers see consistent snapshot. (2) **Time...

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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
Puma

Why This Question Matters

This easy-level Spark/Big Data question appears frequently in data engineering interviews at companies like Puma. While less common, it tests deeper understanding that distinguishes strong candidates.

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Expert Answer
103 words

Why Delta Over Raw Parquet: Parquet is immutable; no deletes, no transactional writes. Concurrent writers create corrupt state. Delta adds transaction log and metadata.

Delta Advantages: (1) ACID—concurrent writes; readers see consistent snapshot. (2) Time travel—versionAsOf, timestampAsOf for audits and rollback. (3) MERGE/UPDATE/DELETE—CDC, upserts without overwrite. (4) Schema enforcement/evolution—reject bad data; add columns safely. (5) OPTIMIZE/VACUUM—compact small files; reclaim storage.

Scalability Trade-offs: Transaction log can grow; checkpoint files and VACUUM manage it. Z-ordering helps reads but costs write time.

Cost Implications: Delta adds ~5–10% storage for log; read performance often better via compaction. Enables use cases (CDC, time travel) impossible with raw Parquet.

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