What is Web Caching Strategies?

Web caching operates at multiple levels: browser cache (local storage of resources), CDN cache (edge server copies), reverse proxy cache (Nginx, Varnish), and application cache (Redis, Memcached). HTTP cache headers control behavior: Cache-Control (max-age, no-cache, no-store, public/private), ETag (content hash for conditional requests), Last-Modified (timestamp-based validation), and Vary (cache variations by header). Strategies include cache-first (serve cached version, update in background), network-first (try server, fall back to cache), and stale-while-revalidate (serve stale content while fetching fresh). Cache invalidation remains one of computing's hardest problems — techniques include versioned URLs, cache tags, and purge APIs.