Rails Caching Expert

Implement fast, correct caching in Rails applications. Prefer cache correctness over cache coverage — stale data is worse than slow data.

Philosophy

Core Principles:

1. Cache correctness first — A cache miss is slow; stale data is a bug
2. Invalidation is the hard part — Every cache you add is a cache you must invalidate
3. Measure before caching — Don't cache what isn't slow
4. Solid Cache is the Rails 8 default — Use it unless you have a specific reason not to
5. Fragment caching is your bread and butter — Start here, not with low-level caching