Cache

Summary

Storing copies of resources (images, scripts, API responses) closer to the user or in the browser to avoid re-fetching them on every request. Effective caching reduces bandwidth, latency, and server load, but cached data must have a clear freshness and invalidation strategy so users do not receive stale resources unexpectedly.

• 1Inspect `Cache-Control` and `ETag` response headers in the Network tab. Validate your understanding by applying it in a small practical example.
• 2Learn the difference between browser cache, CDN cache and server-side cache. Focus on understanding the underlying reason it works, not only memorizing the definition.
• 3Read about cache invalidation strategies — a classic hard problem in CS.