Image Processing in Background

[wolfmoritz]

If a TinyJPG key was provided, on upload the images are processed into five optimized files, all during the upload request. Consider separating upload from optimization, and run the optimization in the background as a separate request to allow the file upload request return a response to the user more quickly, to avoid aborted uploads.

Suggest creating a jobs table, one for each file size, and the background process can run a CLI request to select rows in the jobs table, update the processing flag, create the files, and then clean up the job table.