NGINX / Wordpress Site - Increasing php.ini max_execution_time = 600 doesn't work

There are basically 3 sets of timeouts when dealing with simple NGINX + PHP-FPM stack.

One is PHP engine, which you have already adjusted to unlimited.

Second is PHP-FPM, which is controlled via request_terminate_timeout in your pool settings. The default is usually like this:

;request_terminate_timeout = 0

Value of 0 would mean that there is no limit set by PHP-FPM itself, so you likely won’t have to adjust that.

Finally, there are NGINX timeouts for FastCGI communication, which are controlled through a couple of directives in your NGINX config. You mostly care about fastcgi_read_timeout:

If the FastCGI server does not transmit anything within this time, the connection is closed.

You would place it in your PHP handler location, e.g.:

location ~ \.php$ {
    ...
    fastcgi_connect_timeout 600s;
    fastcgi_pass ...;

P.S. Don’t confuse “Bad Gateway” (502) and “Gateway Time-out” (504) errors. Those are different errors: the former is for a failure to communicate with PHP-FPM (typically a sign of severe misconfiguration, defunct / not running PHP-FPM process), while the latter is exceeding timeout while communicating with PHP-FPM.

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