In their own words : Vercel is a cloud platform for static sites and Serverless Functions that fits perfectly with your workflow. It enables developers to host Jamstack sites and web services that deploy instantly, scale automatically, and requires no supervision, all with no configuration.
We strongly recommend this service as it is serverless, cheap, includes CDN, and really easy to set up.
It also supports the cache technique stale-while-revalidate (which they call Serverless Pre-Rendering). This is a powerful way to improve your site speed.
Vercel now forces all apps to be served over HTTPS. You therefore need to ensure that your WordPress site has a SSL certificate and that you connect to your WordPress API endpoint using HTTPS rather than HTTP.
The effect of using a HTTP only connection on a Frontity project deployed on Vercel will result in navigation links not working and getting stuck in the data.isFetching state (although apparently working on the local dev machine). The reason is that Frontity won't be able to fetch the content from the WordPress backend over HTTP on a pure HTTPS site.