Server side rendering takes time, even 10 ms. On an single event loop, that is terrible. You can only server 100 request/second due to the 10 ms limit. While it is nice that you can move a request into the backing queue while waiting for the data, you're capped at 100 requests/second.

Where I think Node shines is low level network management. Netflix could use it to pipe video data from one of its boxes out to a user. It's got that kind of work built right into it. As a result, I think that storage, spooling and possibly even sending would be best in Node. Those are largely I/O bound, schlep data from port to port operations.

My understanding of PHP is that it's really hard to have really global variables. Compare this to Node.js where Javascript naturally does this. I can't find it now, but I remember back when Node was young a guy had an issue with his shopping cart system. People's orders were screwed up. Turns out that he missed a `var` in a function. PHP, I don't think, could do this easily since the widest screw up scope is file. So you're still limited to request scoping.