Just ran the same WebSocket load tests with #SiteJS on a 2 vCPU VPS with 2GB RAM and it started dropping messages (1 message/sec) at around 10K concurrent connections.
I’m more than happy with that as a starting point. (That’s not what we need to optimise. For context, I have 7.24K followers on the fediverse after 3 years. We won’t start hitting those limits on the #SmallWeb for a while.) ;)
Videos, etc., at: https://twitter.com/aral/status/1345734023658745866
Note: I posted those videos on Twitter as my Mastodon personal instance didn’t let me post them as they were too large (my instance of one is hosted on @mastohost and they have limits – which is understandable; they’re not a multi-billion-dollar company).
For longer videos, etc., I use our Vimeo account.
@aral The limits are set by Mastodon https://github.com/tootsuite/mastodon/blob/master/app/models/media_attachment.rb#L153-L157
I believe the reasoning for this is for one instance not allow 1GB video and another 5MB. Besides creating "special" instances it also would not fully federate between an instance where large videos are allowed and an instance with small videos.
This way every Mastodon instance follows the same limits (as long as the admin didn't hardcode a change to those values).
@aral Obviously, the cost of allowing concurrent streaming of large videos is high and would increase the cost for someone running a Mastodon instance.
I do think these limits make sense. Not sure if the values are ideal but there should be a small limit to make possible running a Mastodon instance on a low cost set up.
@aral It would make sense, at least for uploads done via the web interface of Mastodon. Other software could probably manage that compressing client side.
Having said that, I have spent so many hours dealing with ffmpeg issues...
@aral have you tried using the ImagePipe app on Android? That compresses images automatically
@aral @mastohost We did historically up the limits when a new generation of iPhones dropped because ideally mobile videos should just work but it’s complicated, the bigger they are, the more resources it takes to process it server-side.
@SuperDicq @aral @mastohost Probably not in the browser, though native apps should be able to
Server run by the main developers of the project 
It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!
@mastohost Don’t disagree. I do wonder, however, if more processing could be done server side so that a < 30 second video captured on a modern mobile phone fits the limits (the issue is that modern phones have stellar resolution so they’d need to be resampled/recompressed).