Closing the Loop: Proxy-Aware Rate Limiting With X-Forwarded-For

Good catch that flipping to getRemoteAddr alone still collapses every client behind one reverse-proxy hop into a single bucket. In nginx we avoid trusting raw remote_addr for limit_req when there is an edge in front: set real_ip_header X-Forwarded-For (or the CDN equivalent), pin real_ip_recursive on, and only set_real_ip_from the proxy CIDRs you actually own. Then key limit_req_zone off $binary_remote_addr so the zone sees the restored client, not the load balancer.

Ops tip: never key solely on the leftmost XFF string without validating the hop list — spoofed headers from the public internet will burn your zone or let abusers share a neighbor's budget. Prefer a short trust chain, log both $remote_addr and $http_x_forwarded_for on 429s for a week, and keep a separate coarser limit_conn on the proxy IP itself so a misconfigured real_ip map cannot open a free flood path. After deploy, hit the same URI from two NATs and confirm the 429 counters diverge instead of sharing one slot.