External‑sorting is a Node‑JS library that streams large data sets (strings, numbers or JSON objects) from an input file, sorts them with configurable keys and order, and writes the result to an output file using only a small memory footprint (via temporary files and a limited‑size heap). It’s aimed at developers who need to sort data that exceeds available RAM, such as batch processing or ETL pipelines, and provides a simple API with custom serializers, delimiters and multi‑field sorting.