Your "Cache Invalidation is Hard" Answer Misses the Real Horror

Your "Cache Invalidation is Hard" Answer Misses the Real Horror Most engineers parrot "cache invalidation is hard" as a standard interview response, but few understand why it's hard or the real-world horrors it introduces. It's not just about stale data; it's about financial losses, broken business logic, and cascading failures when eventual consistency hits critical paths. The Production Nightmare: Financial Impact of Stale Data Imagine a ride-sharing platform like Uber. A user updates their pa