How does Scala support multi-layer caching coherence in distributed systems?

Cache coherence is maintained using invalidation strategies, TTL policies, and event-driven updates.

Scala systems implement multi-layer caching (L1 local, L2 distributed, CDN edge). Maintaining coherence requires invalidation strategies triggered by domain events. Write-through or write-behind patterns ensure updates propagate correctly. Event-driven cache invalidation via Kafka ensures all nodes receive updates. TTL policies reduce stale data risks but introduce eventual consistency trade-offs.