Optimal web server settings (nginx->apache->php) for api?

Question

PHP

Hello. Debian8 machine, 4gb, 2x2.6ghz.
Now the web server is installed according to the scheme nginx -> apache2 -> php5.6 (provided by means of vestacp).
Service - handler of callback requests. In prime time, up to 300 incoming http requests per second, we give a response to them and at the same time send ~ 10 outgoing requests per second.
No website, no statics. Nginx in primetime uses 2 processes and eats each of the cores by 15-20%.
For days now I have been thinking that the configuration of my web server is at least wrong. Doesn't really suit my purposes.
Vyzhadminy, clarify what web server configuration will be optimal for this task?
(by configuration, I mean nginx+apache, nginx+php-fpm, bare apache, etc., I'm sorry if I'm wrong in the terminology)

Answer 1

Purely empirically - the Apache is superfluous in a bunch.
There was such a question here Apache vs Ngnix + FastCGI vs Ngnix + Apache - which is more productive for php?

Answer 2

You can read about setting up nginx here