Apache .conf file ignored

I'm running Apache Apache/2.4.25 (Amazon) using prefork and I'm trying to adjust ServerLimit and MaxRequestWorkers. I'm using the following settings:

<IfModule prefork.c> ServerLimit 40 MaxRequestWorkers 40 </IfModule>

The problem is that if I add these settings in /etc/http/conf.d/prefork.conf, they are ignored despite the general /etc/httpd/conf/httpd.conf having the following directive set:

IncludeOptional conf.d/*.conf

Other configuration files present in conf.d/ seem to be parsed but not this one. So, the only way I could adjust the limits is by editing /etc/httpd/conf/httpd.conf directly and placing the above. Why are the values not read from a conf.d/*.conf file? Has anyone else ran into this issue? Any help would be appreciated. Thank you.

Did you check the permissions of /etc/http/conf.d/prefork.conf. If you created the file as root or another user and the permissions aren't o+r, apache user might not be able to read the file.

This would probably be visible in server logs.

Another problem might be that if the ServerRoot is not set to /etc/http/, the IncludeOptional would not work. You can try setting it to a full path:

IncludeOptional /etc/http/conf.d/*.conf