HTTP Caching Primer

Core idea

Caching reduces repeated work, but only when cache headers clearly express freshness and validation rules.

Revision points

• Cache-Control defines freshness.
• ETag and If-None-Match support validation.
• Not every endpoint should be cached the same way.

Cache-Control: public, max-age=60, stale-while-revalidate=120
ETag: "notes-101-v1"

What to remember

Cache policy is part of API design, not an afterthought.