Url shortener using nginx and lua

nginx.conf

events {}

http {
  upstream pgdb {
    postgres_server urlshortnertestdb.cccccccccccc.us-west-2.rds.amazonaws.com dbname=redirect  user=root password=password;
  }

  server {
    listen 80;
    server_name localhost;
    
    location /admin/ {
      uwsgi_pass   unix:///tmp/uwsgi.sock;
      include      /home/ubuntu/urlshortner/server_files/conf/uwsgi_params;
    }

    location ~ "^/([0-9a-zA-Z]{18})\/{0,1}$" {
        content_by_lua '
           local query_string = string.gsub(ngx.var.request_uri, "/", "");
           local referer = ngx.var.http_referer;
           local res = ngx.location.capture("/lookup",
             { args = { query = query_string  } }
           );
            ngx.location.capture("/increment",
             { args = { query = query_string } }
           );
           ngx.location.capture("/log",
             { args = { query = query_string } }
           );
           ngx.redirect(res.body);
        ';
    }

    location /lookup {
      internal;
      postgres_pass pgdb;
      postgres_escape $esc_uid $arg_query;
      postgres_query GET "SELECT \"Output\" FROM \"Redirect_redirecturl\" WHERE \"Input\" = $esc_uid;";
      postgres_output text;
    }

    location /log {
      internal;
      postgres_pass pgdb;
      postgres_escape $esc_uid $arg_query;
      postgres_escape $referencia $http_referer;
      postgres_escape $user_agent $http_user_agent;
      postgres_query GET "INSERT INTO \"Redirect_visit\" (\"Created\",\"RedirectUrl_id\",\"Referer\",\"UserAgent\") SELECT now(), ID, $referencia, $user_agent FROM \"Redirect_redirecturl\" WHERE \"Input\" = $esc_uid;";
    }

    location /increment {
      internal;
      postgres_pass pgdb;
      postgres_escape $esc_uid $arg_query;
      postgres_query GET "UPDATE \"Redirect_redirecturl\" SET  \"Counter\" = \"Counter\" + 1 WHERE \"Input\" = $esc_uid;";
      postgres_output none;
    }

    location ~ ^/add {
      postgres_pass pgdb;
      rds_json on;
      postgres_escape $url $arg_url;
      postgres_query GET "INSERT INTO redirect_redirecturl (input, output) VALUES((SELECT substring(md5(random()::text||$url), 0, 5)), $url) RETURNING input;";
      postgres_output text;
      postgres_rewrite GET changes 201;
    }
  }
}