Astro
Vercel adapter
Vercel adapter is the Astro adapter that outputs your on-demand routes in Vercel's build format. Static files are served from the edge network.
How it is measured
Add @astrojs/vercel and register it. The build writes a .vercel/output folder with functions and static assets. Options cover image service, web analytics, and incremental static regeneration.
Check on a preview deployment. The Vercel dashboard lists each function. Look at the duration and memory of one on-demand route.
Worked example
A film-festival site has a /schedule route that depends on a feed. With ISR set to 300 seconds, the page is regenerated at most once every 5 minutes. A burst of 8,000 visits that hour causes 12 renders.
The team had earlier left ISR off, and each visit triggered a function call. The bill showed it in the next cycle.
How it differs
The Vercel adapter emits Vercel's function format. The Netlify adapter emits Netlify's. Each excludes the other host's config files and platform features.
Common errors
Mixing up hosts and adapters. Forgetting function limits. Leaving ISR off for pages that can be cached. Using the Vercel image service in a project that does not need it. Skipping environment variables on preview.
In practice
Mark routes as static where possible. Turn on ISR for pages that tolerate a few minutes of age. Check the function list after each deploy.