Spreadsheet export errors

Every page here answers one error properly: why it happens, then the fix in the library you are already using. Jarrah is mentioned last, and only because it is a real option, not because the page needs you to take it.

• Allowed memory size of 134217728 bytes exhausted (PHPSpreadsheet) PHPSpreadsheet holds every cell in memory as an object. Measured numbers, the cell-cache fix, and the streaming writer that does a million rows in 2 MB.
• Laravel Excel: allowed memory size exhausted, or maximum execution time of 30 seconds exceeded FromQuery buys about 5,000 rows, not the 90% everyone expects. Measured peaks for FromCollection, FromQuery, cell caching and OpenSpout on Laravel 13.