Error Upstream Timeout

i config kong.conf + Gui as below and some time output error " upstream timed out ( 110 : Connection timed out)", who can help me ?
1/ kong.conf
nginx_http_keepalive_timeout=3000s
nginx_proxy_proxy_read_timeout=3000s
nginx_http_proxy_read_timeout=3000s
nginx_proxy_send_timeout=3000s
nginx_http_send_timeout=3000s
2/ Gui APIs:
upstream_connect_timout = 600000ms
upstream_send_timout = 600000ms
upstream_read_timout = 600000ms

Thanks,