Workflow: protecting a public API on Cloudflare
# Workflow: API protection
## 1. Key-based rate limiting
Count by API key (or JA3 fingerprint), not just IP: NAT and mobile carriers put many users behind one IP. Deploy in Log mode, pick thresholds from the request-rate analysis, then enforce. Count failures for auth endpoints.
## 2. WAF custom rules for abuse
Block known-bad patterns (credential stuffing paths, scanner user agents) with narrow rules. Skip rules for your own monitoring and partner integrations go first.
## 3. Cache rules: never cache authenticated responses
The dangerous misconfiguration: a Cache Rule caching `/api/*` that serves one user's data to everyone. Cache only unauthenticated, public endpoints, and key the cache to exclude Authorization headers. When in doubt, DYNAMIC (do not cache) for anything behind auth.
## 4. Origin protection
The API origin should only accept traffic from Cloudflare IPs (allowlist) so attackers cannot bypass the WAF by hitting the origin directly. Authenticated origin pulls (TLS client certs) make this airtight.
## 5. Observability
Tail the Worker (if the API runs on Workers) or watch origin logs with the real client IP restored via `CF-Connecting-IP`. Alert on 429 spikes (rate limit too tight) and 403 spikes (WAF false positives).
## Checklist
- Rate limit by key, WAF for patterns, cache never for authed responses.
- Origin locked to Cloudflare IPs.
- 429/403 spikes are the tuning signals.Find related guidance
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