$upstream_response_time > fastcgi_connect_timeout + fastcgi_read_timeout ?

[hammer]

hi:

we have a server dealing with big traffic, so I decide to cut slow
request by timeout:

                        fastcgi_connect_timeout 5ms;
                        fastcgi_read_timeout 10ms;

however, I still see log requests where upstream_response_time = 1.894
second

so why?

I have manually verified the config. the server responses 504 when the
request is slow.