How do you handle content updates with a CDN?

Strategies: cache versioning (include version/hash in URL - new URL bypasses cache), TTL-based (set appropriate expiration - balance freshness vs hit rate), purge/invalidation API (explicitly clear cache - propagation delay), stale-while-revalidate (serve stale while fetching fresh). Best practices: long TTL + versioned URLs for static assets, shorter TTL for dynamic content, use cache tags for grouped invalidation. Consider: invalidation cost, edge propagation time, origin shield (reduce origin load). Different strategies for different content types.