CloudFlare is build on top of OpenResty which is basically stock nginx with ngx_lua and a bunch of other modules built in. I would argue that if you want it to be, nginx can be much better at DDoS mitigation. You can use the modules limit_conn and limit_req to control how many connection individual IPs can make to your server for basic control.

You can add various things on top of nginx... but you can use stock haproxy to limit the number of connections by source IP.

This can also be achieved in nginx fairly easy:

http://nginx.org/en/docs/http/ngx_http_limit_conn_module.htm...