CF can cause a small DoS as it does some aggressive pre-fetching. So your server...

jjoe on Nov 1, 2013 | parent | context | favorite | on: Ask PG: Is HN experiencing server problems?

CF can cause a small DoS as it does some aggressive pre-fetching. So your server needs to handle short bursts really well. Not to mention whitelist CF's IP space both in the firewall and nginx rate limiting.