Rack::Attack - Rack middleware for blocking & throttling abusive requests

iptables
    |
   V
nginx  -   ngx_http_limit_conn_module
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   V
rack middleware - rack attack

Iptables:
https://duckduckgo.com/?q=iptables&t=brave&ia=web

Nginx ngx_http_limit_conn_module:
https://nginx.org/en/docs/http/ngx_http_limit_conn_module.html#limit_conn_zone

Rack Attack links:
https://github.com/kickstarter/rack-attack
https://kickstarter.engineering/rack-attack-protection-from-abusive-clients-4c188496293b
https://blog.bigbinary.com/2018/05/15/how-to-mitigate-ddos-using-rack-attack.html
https://dylanwolff.com/posts/blocking-abusive-requests-to-your-ruby-app-with-rack-attack/
http://blog.hayleyanderson.us/2015/06/05/using-and-testing-rack-attack-to-improve-the-security-of-your-rails-app/