Cache invalidation is notoriously difficult to get right in high-throughput systems.
If your cache TTL is too short (e.g. 10 seconds), your database gets overwhelmed by stampedes. If your TTL is too long (e.g. 24 hours), your application serves stale data after updates.
The standard solution is event-driven cache invalidation. Whenever a mutation occurs in your CMS, e-commerce admin, or custom backend, you trigger an invalidation webhook that purges matching cache entries across all edge points of presence.
Here is how to design a resilient, zero-downtime cache invalidation pipeline with surrogate key tags, fanout workers, and retry guarantees.
1. Surrogate Key Tags (The Tagging Hierarchy)
