deangrant HTTP Caching and Conditional Requests
Use this skill when making safe GETs cheaper via caches and validators.
1. Cache-Control
Common directives: max-age, s-maxage (shared), private / public,
no-store, must-revalidate, stale-while-revalidate.
User-specific data: private + Vary: Authorization (or equivalent).
2. Validators
Strong ETag (or Last-Modified). Client sends If-None-Match → 304
when unchanged. Pair with caching for revalidation.
Mutations and contested updates use If-Match (see conditional-requests skill).
3. Quick checklist
- Cache-Control correct for public vs private data.
- ETag or Last-Modified on cacheable GETs.
- 304 path implemented.
- Vary set when representation differs by header.
- No caching of sensitive responses on shared caches.
See reference.md and examples.md.