#1: I suggest you go for a cron job. Assuming you store the file name in a database, you could also set a status for it: like 0 - not processed, 1 - processing ok, -1 - invalid file. Then, the cron job pulls the first 50 files added (or less, depending on your needs), and updates the status for each file processed. Then, you would display only the files with the status '1' on your page.

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