Introduction Overly aggressive rate limiting on load balancers blocks legitimate users, causing 429 Too Many Requests errors and degraded user experience.

Symptoms - Legitimate users receiving 429 Too Many Requests - Rate limit hit rate unusually high - Users on same NAT/CGNAT all blocked together - API clients hitting limits with normal usage - Complaints about intermittent access issues

Common Causes - Rate limit threshold too low for normal usage - Rate limiting based on IP (CGNAT sharing issue) - No burst allowance for legitimate traffic spikes - Rate limit reset period too long - Rate limiting applied to authentication endpoints

Step-by-Step Fix 1. **Check current rate limit configuration': ```nginx # Nginx rate limiting limit_req_zone $binary_remote_addr zone=api:10m rate=30r/s; # Increase if too low limit_req_zone $binary_remote_addr zone=api:10m rate=100r/s; ```

  1. 1.**Add burst allowance':
  2. 2.```nginx
  3. 3.limit_req zone=api burst=50 nodelay;
  4. 4.`
  5. 5.**Use token-based rate limiting for APIs':
  6. 6.Implement API key-based rate limiting instead of IP-based.

Prevention - Set rate limits based on actual usage analytics - Use API keys for more accurate client identification - Implement graduated rate limiting (warn before block) - Monitor rate limit hit rate and adjust accordingly - Allowlist known legitimate high-traffic clients