docs: cacheHandlers

[icyJoseph]

No description provided.

[apostolos]

"Persistent cache across deployments"

Is this accurate?

Cache keys are namespaced (with the build id)!

Everything else remaining the same, new deployments will never see the previously stored keys and miss.

[icyJoseph]

Looking into it! Thanks for the input!

[apostolos]

We'd love to be able to do this, don't get me wrong. I guess someone could parse the key and work around it, but keys are supposed to be opaque and understandably so.

It's a great to have feature, until it isn't (schema changes).

In an ideal world, instead of namespacing by build id another concept could be introduced. Maybe a "schema version". Cached data could then be safely shared across deployments.

[icyJoseph]

So I was reading a bit and the reason is

next.js/packages/next/src/server/use-cache/use-cache-wrapper.ts

Lines 991 to 995 in 498349c

	// Because the Action ID is not yet unique per implementation of that Action we can't
	// safely reuse the results across builds yet. In the meantime we add the buildId to the
	// arguments as a seed to ensure they're not reused. Remove this once Action IDs hash
	// the implementation.
	const buildId = workStore.buildId

I'll update accordingly for now, but will check again w/ team on Monday.