How does Scala support hierarchical distributed caching with consistency guarantees?

Scala systems use multi-level caching (L1/L2/L3) with invalidation, TTLs, and event-driven synchronization.

Hierarchical caching in Scala architectures involves local in-memory caches (Caffeine/Guava), distributed caches (Redis/Memcached), and persistent stores. Consistency is maintained using event-driven invalidation (Kafka topics), write-through or write-behind strategies, and TTL-based fallback expiry. Cache stampede protection uses locking or request coalescing. Trade-offs exist between consistency, latency, and availability.