How does Rails handle large-scale system-wide caching invalidation strategies?

Rails uses event-driven invalidation, cache versioning, and pub-sub mechanisms to manage cache consistency.

Cache invalidation at scale is one of the hardest distributed systems problems. Rails uses multiple strategies: versioned cache keys to avoid direct invalidation, pub-sub systems like Redis or Kafka to broadcast invalidation events, and TTL-based expiration. Some systems also use write-through caching where updates immediately refresh cache entries.