I'm quite sad about this, there was one thing that push was great for, and thats optimizing pageload speeds for first-time visitors.
We used it to push about ~140kb of static assets before our django views finished computing, and it noticeably sped up initial pageload speed for first-time visitors, which is the segment we cared most about.
It's a powerful footgun, obviously it will only make things worse if you're pushing multiple megabytes of JS to users who already have it cached, but when used sparingly in the right situations it was quite helpful.
One place where I can still see this working well is landing pages for marketing campaigns; it’s a fair assumption that most visitors there will be first time visitors.
Other than that, I’d say that there should be a mechanism where the browser informs the server of what assets they have cached, although I can only assume that may open a privacy can of worms.
We used it to push about ~140kb of static assets before our django views finished computing, and it noticeably sped up initial pageload speed for first-time visitors, which is the segment we cared most about.
It's a powerful footgun, obviously it will only make things worse if you're pushing multiple megabytes of JS to users who already have it cached, but when used sparingly in the right situations it was quite helpful.
I even built a django middleware that handled figuring out which assets to push automatically: https://github.com/pirate/django-http2-middleware