Do the upstream PHP servers have to run the same server software?If I have the following Nginx configuration upstream myapp1 {        server srv1.example.com;        server srv2.example.com;    }Assuming we have shared back-end database and identical web sites, could I use Apache on srv1 and PHP-FPM on srv2 to compare the two under identical real-world load?
Nginx loadbalancing between PHP-FPM and Apache
nginx