Symphony.

XSLT is not cached by APC

What a shame. I never thought about that, because it's still lightning fast if you use the server's HardDrive.

Aha, seems that even the New York Times knows the issue.

I'm sure if someone asked fortrabbit they would look at making XSL Cache available?

There are other PaaS as well that are providing similar features as Fortrabbit, like Cloudways. They also provide SSH+SFTP access, Git deployment, Free SSL certificate, scalability. You can install Symphony on AWS, GCE, Vultr or DigitalOcean using PHPStack option on Cloudways.