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How would you prevent small file problems in S3 when loading data into Redshift?

SQLmedium0.6 min readPremium
Frequency
Low
Asked at 1 company
Category
487
questions in SQL
Difficulty Split
130E|271M|86H
in this category
Total Bank
1,863
across 7 categories
Asked at these companies
Capco
Key Concepts Tested
etlpartitionspark
Expert AnswerPremium
121 wordsInterview-ready
Small files in S3 cause Redshift COPY slowdowns (each file triggers a slice). Solutions: (1) Coalesce before load—run a Spark/Glue job to merge files (e.g., 128MB per file). (2) Use manifest files—COPY from a manifest listing fewer, larger files. (3) Enable MANIFEST in Glue/ETL to output fewer parts. (4) Buffer in Kinesis Firehose with size/count thresholds. (5) Use Redshift Spectrum for ad-hoc S3 queries without loading. Best practice: target 1–128MB files per Redshift slice....
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