S3 Select lets you retrieve only a subset of data from an object using SQL, instead of downloading the whole file. For large CSV, JSON, or Parquet objects, that means less data transferred and faster, cheaper queries.
The tell
When an application needs a few rows or columns from large S3 objects and you want to avoid pulling the entire file, that’s S3 Select. It pushes the filtering into S3. Distinguish from Athena (queries across many objects/tables); S3 Select works on a single object.
Test yourself
An application needs only a few columns from large CSV files in S3 and wants to avoid downloading the entire files. What’s the most efficient approach?
- Download each full file and filter locally
- Use S3 Select to retrieve only the needed data with SQL
- Copy the files to EBS first
- Enable S3 Transfer Acceleration
👉 Click to reveal the answer & explanation
Correct answer: B. S3 Select uses SQL to return only the needed subset from an object, cutting data transferred and cost. Downloading full files (A) wastes bandwidth; copying to EBS (C) still transfers everything; Transfer Acceleration (D) speeds transfer but doesn’t reduce data.
Related topics
Amazon S3 · Amazon Athena · Parquet vs ORC vs CSV
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