What is the number of TCP connections, the number of requests is the norm?

Question

Highload

Hello!
Problem: a site with images is periodically parsed, completely and completely. It copes with the load, everything is ok, but the clients who use it at this moment are not very satisfied with the speed of its work, I would like to protect myself.
Server: Nginx
Planned to use ngx_http_limit_req_module module.
What kind of indicators should be for the site:
- the number of TCP connections from one IP
- the number of requests from one IP
, etc.
I understand that exactly you need to look at yourself how many are now at rest and roughly estimate what indicators will be, say, with a light load or DDOS. But still, maybe someone has useful information.

Answer 1

I set about 10 requests per second with 1 SP with 5
burst limit_req_zone $binary_remote_addr zone=ips:10m rate=10r/s;
location /..... {
limit_req zone=ips burst=5;
}