[CentOS] Is decoupling Apache + PHP into separate nodes possible?

<preamble>
I have deployed Linux/Apache/PHP (node1) + MySQL (node2) with Security
Groups (AWS) or iptables controlling who can connect to the MySQL
server.   In topology terms -- a 2 Tier architecture.  In AWS - one
can deploy several such instances behind a ELB.  Each LAP instance
talks to a MySQL RDS.  The LAP instances are either mod_php or
PHP-FPM.  OS -- CentOS, Ubuntu. Debian
</preamble>

For one of my client's end user customer, their InfoSec team is asking
if Apache and the PHP application can run in separate nodes (3 Tier
arch).

To the best of my knowledge Apache + PHP (mod_php) have to be in the same node.

With PHP-FPM it is conceivable to have Apache talk to PHP-FPM running
on a separate node (see diagram https://goo.gl/xTfbjg).
But I have not done it myself and I am not sure if it is feasible.

If it is feasible then what's the best practice to  distribute the
*.html *.css and *.php files between the Apache + the PHP-FPM nodes
and how to achieve load balance between Apache and PHP-FPM nodes.  I
have searched but not found any reference setups.

Would appreciate suggestions / references from anyone who has done a 3
Tier Apache + PHP + MySQL deployment in production.

Thanks in advance.

--
Arun Khan
"Everyone has an expiration date"