How to protect against multiple POST requests in nginx?

Question

Nginx

Hello!
For example, there is a url "/sms-auth", there is a sending form for authorization by SMS.
Need advice on securing this url from multiple POST requests.
Is it possible to protect yourself with nginx methods or is there another thread to look at?
Who faced such problems? What can you advise?
Many thanks in advance for any help.

Answer 1

protect successful form submit, captcha

Answer 2

Read about testcookies.
You can also set up a bunch of fail2ban and limit the rate of requests to the form