gzip on;
gzip_buffers 16 8k;
gzip_comp_level 9;
gzip_min_length 100;
gzip_vary on;
gzip_types application/atom+xml application/javascript application/json application/rss+xml application/vnd.ms-fontobject application/x-font-ttf application/x-web-app-manifest+json application/xhtml+xml application/xml font/opentype image/svg+xml image/x-icon text/css text/plain text/x-component image/jpg image/png;

Ala, y sin Guetzli.

Edito: Si a esto le añades Nginx con FPM, memcached y te haces un buen .htaccess configurando bien los expires tu web carga en menos de 2 segundos.