Leonid, 

Here are a couple sites with code examples.  It is referred to as "chunking" by some.  Upload scripts that utilize this method has been around for at least 15 years.  I would expect any social media platform that allows uploads of videos to utilize this methodology.  Is it something we can get into the UNA 12 final release or added as a module?

https://code-boxx.com/upload-large-files-php/
https://www.tutorialspoint.com/how-to-upload-large-files-above-500mb-in-php