Do you have anything to say about EFS and WordPress (or other PHP CMS that are basically designed for a single instance?)

Latency on stat() - PHP is often a oop-monster these days with thousands of fs reads as it loads the code? (there are certainly ways to dodge that overhead though).

Have you seen the filesystem stall for any reason? Any caveats with concurrent writers (such as cache/ directories or generated images with deterministic paths etc).

You say without frustrating patches - are there any general limitations with using EFS?

Have you used self-managed NFS for the same purpose before? Any comparison with EFS?