Explain advanced cache consistency models and invalidation strategies in large PHP architectures.

Cache consistency models define how cached data stays synchronized with source systems, balancing performance and correctness.

Caching improves performance but introduces consistency challenges across distributed systems.

Consistency models:

Cache always reflects latest DB state (rare, expensive).

Cache may lag behind database updates.

Cache loads data on miss.

Writes update cache and DB synchronously.

Cache writes asynchronously to DB.

Invalidation strategies:

Simple but can serve stale data.

Domain events invalidate cache entries.…