I'm curious if this would be performant enough to use in something like Heroku. For example a big challenge to running Wordpress on Heroku is that some plugins write out some files, etc
I don't see why not. It only loads a few objects into memory so the footprint would be tiny, especially when you compare it to running WP.
If you can configure the paths these plugins write to, then you can use VFS. Unless the plugin explicitly uses `file://` or they strip the scheme, but I doubt they would.
If you can configure the paths these plugins write to, then you can use VFS. Unless the plugin explicitly uses `file://` or they strip the scheme, but I doubt they would.