Comment by thayne

It isn't that hard to set up naive rate limiting per ip address. It's a few lines in haproxy, and there is documentation on how to do it. There are a couple of problems that make it more complicated though. The first is that with NATs, you can have a lot of users behind a single IP address, which can result in legitimate requests getting blocked. The second is that, while it can help against a DoS, it doesn't help that much against a DDoS, because the requests are coming from a large number of distinct IP addreesses.