Consider using SXSSWorkbook for reading xlsx files

[koperagen]

xssfworkbook keeps whole file in memory, which for even relatively small dataframes or 100k rows can lead to a very significant memory consumption. sxssfworkbook implements streaming writing and flushes rows on disk as you write them. For comparison, max heap writing dataFrameOf('a'..'z').fill(1_000_000) { it }:
xssfworkbook 15 gb
sxssfworkbook 1.6 gb

The only concern is some potential incompatibilities mentioned in javadoc here:
https://poi.apache.org/apidocs/dev/org/apache/poi/xssf/streaming/SXSSFWorkbook.html

Other than that, from user perspective df.writeExcel(file) will benefit from much smaller memory consumption without lose of functionality:
https://poi.apache.org/components/spreadsheet/
https://stackoverflow.com/questions/33047512/hssfworkbook-vs-xssfworkbook-vs-sxssfworkbook-apache-poi

Check some other JVM DF libraries, do they use it?