AWS WAF How to rate limit path by IP below the minimum of 2000 requests/minute

AWS have now finally released an update which allows the rate limit to go as low as 100 requests every 5 minutes.

Announcement post: https://aws.amazon.com/about-aws/whats-new/2019/08/lower-threshold-for-aws-waf-rate-based-rules/

I don't know if this is still useful to you - but I just got a tip from AWS support. If you add the rate limit rule multiple times, it effectively reduces the number of requests each time. Basically what happens is each time you add the rule, it counts an extra request for each IP. So say an IP makes a single request. If you have 2 rate limit rules applied, the request is counted twice. So basically, instead of 2000 requests, the IP only has to make 1000 before it gets blocked. If you add 3 rules, it will count each request 3 times - so the IP will be blocked at 667 requests.

The other thing they clarified is that the "window" is 5 minutes, but if the total is breached anywhere in that window, it will be blocked. I thought the WAF would only evaluate the requests after a 5 minute period. So for example. Say you have a single rule for 2000 requests in 5 minutes. Say an IP makes 2000 requests in the 1st minute, then only 10 requests after that for the next 4 minutes. I initially understood that the IP would only be blocked after minute 5 (because WAF evaluates a 5 minute window). But apparently, if the IP exceeds the limit anywhere in that window, it will be locked immediately. So if that IP makes 2000 requests in minute 1, it will actually be blocked from minute 2, 3, 4 and 5. But then will be allowed again from minute 6 onward. This clarified a lot for me. Having said that, I haven't tested this yet. I assume the AWS support techie knows what he's talking about - but definitely worth testing first.