Edge DDoS Mitigation Under Election-Cycle Load
Profile:High-traffic political opinion publisher
Coordinated L7 attacks during a presidential election cycle threatened to take a national opinion publisher offline at peak ad-revenue hours. Designed and rolled out a layered edge defense without breaking caching for legitimate readers.
Key results
The problem
A national political opinion publisher receives organic traffic spikes of 10-20x baseline during election cycles. On top of that organic spike, coordinated L7 attacks (low-and-slow POST floods, distributed bot crawls hitting search endpoints, and credential stuffing on the comment subsystem) were threatening to take the site offline at exactly the hours where ad revenue peaks.
The baseline stack — Cloudflare in front of an origin running Varnish + WordPress — was tuned for read-heavy traffic, not adversarial workloads.
The approach
Layered defense, configured live during the cycle:
Cloudflare WAF custom rules to block known attack signatures by ASN, country and request shape, with explicit allowlists for legitimate ad-tech and analytics partners.
Rate limiting on POST endpoints (search, comments, login) with per-IP and per-ASN buckets — tight enough to break the attack, loose enough to not break a school running NAT.
Bot Fight Mode + managed challenge on suspicious paths.
VCL hardening on Varnish: normalized cache keys to kill cache-busting attacks, added stale-while-revalidate to absorb backend pressure, and split hot vs cold object pools so a flood on one section couldn't evict the homepage.
Real-time monitoring with synthetic checks from 4 regions plus log-based alerting on 5xx surges.
Every rule was promoted through staging first and rolled forward with a 5-minute observation window. No big-bang changes during a high-stakes window.
The outcome
The site stayed up through every attack burst with no measurable revenue impact. Edge TTFB held under 50ms for legitimate readers. The ruleset was documented and handed off to the in-house ops team with runbooks for the next cycle.
Why it matters
During elections, opinion publishers are both more visible and more contested. The interesting engineering is keeping the site fast for genuine readers while the attack layer absorbs everything else — without a single false positive blocking a real reader trying to vote-check a claim.
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