Convert FEATHER to JSONL

Feather is a fast, lightweight binary columnar data format jointly developed by the Apache Arrow and pandas teams for efficient data interchange between Python and R. It leverages Apache Arrow's in-memory columnar format to achieve extremely fast read and write speeds with good compression. Feather is optimized for performance rather than long-term archival and is ideal for sharing large data frames between data science tools in a pipeline.

JSONL (JSON Lines, also known as NDJSON) stores one complete, valid JSON object per line in a plain-text file. This line-by-line structure makes it ideal for streaming large datasets, log files, and machine learning training data, since each record can be processed independently without loading the entire file into memory. JSONL is increasingly standard in data engineering, LLM training pipelines, and high-throughput logging systems.