<b>This week in caching: the Vary header, the quiet hit-rate killer</b>

<b>This week in caching: the Vary header, the quiet hit-rate killer</b>
Small header, outsized damage. Curated:
— <i>Vary: Accept-Encoding done right</i> — the one Vary value you almost always want, and why normalizing it matters.
— <i>Vary: Cookie = no cache</i> — how a single cookie in the Vary list effectively disables shared caching.
— <i>Key normalization instead of Vary</i> — CDN cache-key rules as a surgical alternative to fragmenting on a full header.
— <i>Client Hints and the future of Vary</i> — how Vary: Sec-CH-* changes responsive image caching.
Credits to the MDN docs and Andrew Betts' edge-caching talks.
Bookmark: the cache-key-vs-Vary comparison — the trick that recovers a tanked hit ratio.