Vercel caching proof of concept

The implementation uses Vercel’s content delivery network (CDN) to cache public HTML and client-navigation responses.

Response policy

The applyCDNHeaders middleware runs on the public catch-all route and its rendering server function. It sets Vercel-CDN-Cache-Control to a one-year cache lifetime for GET requests without cookies, authorization, or range headers. Other requests receive private, no-store. It leaves the browser cache policy unchanged and adds Accept and X-TSR-ServerFn to Vary.

Only cache public content when the entire response, including the app shell, is identical for all visitors. A cache hit skips the app server and its permission checks. Checking cookies at the app server cannot protect private content on a cache hit.

Invalidation

The custom Plugin uses pageTag from @oberoncms/core to create a stable cache tag for each Page key. It calls addCacheTag from @vercel/functions before reading Page data, including missing Pages.

After Page creation, publication, or deletion, the custom Plugin calls invalidateByTag for that Page. This asks Vercel to mark matching cached responses as stale without invalidating unrelated Pages. Vercel can serve stale content while it generates a new response. An invalidation error causes the action to report a failure.

The Tailwind Plugin keeps previous stylesheet URLs available, so cached Pages can continue to use them.

Limits

The cache hooks do not run during Oberon bootstrap. The Vercel SDK cache methods do nothing without Vercel’s request context.

Publish-triggered cache invalidation has not been verified on Vercel.

See TanStack ISR  and Vercel cache tagging and invalidation .