Cache Invalidation Strategies

Summary

Deciding when cached data becomes stale and needs to be refreshed or removed — TTL expiry, explicit invalidation on writes, or event-driven invalidation.

• 1Implement explicit cache invalidation: clear a cache key whenever the underlying data updates.
• 2Compare TTL-based expiry vs explicit invalidation for a specific use case.
• 3Learn why 'cache invalidation is one of the two hard problems in computer science' is a real, not just a joke.