Pentesting

Rate Limit Bypass

Using similar endpoints

If you are attacking the /api/v3/sign-up endpoint try to perform bruteforce to /Sing-up, /SignUp, /singup...

Also try appending to the original endpoint bytes like %00, %0d%0a, %0d, %0a, %09, %0C, %20

Changing IP origin using headers

X-Originating-IP: 127.0.0.1
X-Forwarded-For: 127.0.0.1
X-Remote-IP: 127.0.0.1
X-Remote-Addr: 127.0.0.1
#or use double X-Forwared-For header
X-Forwarded-For:
X-Forwarded-For: 127.0.0.1

If they are limiting to 10 tries per IP, every 10 tries change the IP inside the header.

Change other headers

Try changing the user-agent, the cookies... anything that could be able to identify you.