<b>Marketing tags shattered the cache</b>

<b>Marketing tags shattered the cache</b>

A travel booking site in Amsterdam couldn't break a 48% cache-hit ratio no matter how long they set TTLs. The pages were cacheable. The problem was that every ad click arrived with a different utm_content and fbclid string, and the CDN keyed the cache on the full URL. The same destination guide got cached thousands of times, once per unique tracking tag, and almost every visitor still missed.

We rewrote the cache key to ignore marketing parameters while passing them through to analytics untouched. Suddenly all those clicks mapped to one cached object.

Cache-hit ratio jumped 48% to 96% overnight. Origin requests dropped 89%. Average TTFB across Europe fell from 310 ms to 70 ms because nearly everyone now hit warm.

The number that mattered: thousands of cache copies collapsed into 1.