During a performance review of a cloud-based data lake, engineers notice that most analytical queries read only a handful of numeric columns out of hundreds stored in high-volume IoT event logs that arrive as nested JSON objects. They want to cut scan time and storage costs by converting the raw ingestion files to a different format. The ideal replacement format must preserve the events' nested schema, enable column pruning and predicate push-down for efficient querying, and provide high compression without hurting read performance. Which file format best satisfies all of these requirements?
Serialize the events as Apache Avro binary files.
Keep the events as RFC 4180-compliant CSV text to maximize compatibility.
Compress the existing JSON files using GZIP without changing the file format.
Convert the events to Apache Parquet files (for example, with Snappy compression).
Apache Parquet is a columnar storage format that keeps data for each column together on disk, allowing analytical engines to read only the columns referenced in a query. This layout supports predicate push-down and achieves superior compression through techniques such as dictionary and run-length encoding while still retaining metadata for complex, nested schemas. CSV and GZIP-compressed JSON are row-oriented text formats that require scanning every column in every row and carry no embedded schema information, so they offer poor compression and no column pruning. Avro embeds a schema but stores records row-by-row, making it efficient for streaming writes yet inefficient for read-heavy analytical workloads where only a subset of columns is needed. Therefore, converting the data to Parquet meets all stated goals.
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