When trying to use the server side search demo at https://reach.tech/combobox/#server-side-search the fetch to https://city-search.now.sh/? is returning the error:
Access to fetch at 'https://city-search.now.sh/?testing' from origin 'https://reach.tech' has been blocked by CORS policy: No 'Access-Control-Allow-Origin' header is present on the requested resource. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
When using the live demo in the documentation the result is always "No results found" because there is a CORS error

Hmm looks like the service itself is actually down; I get a 404 DEPLOYMENT_NOT_FOUND error when attempting to hit the endpoint directly. @chaance do you know what's going on here?
@indiesquidge Looks like something Ryan set up a while ago on Now v1, which is no longer supported by Vercel. I'll see if we can get it up elsewhere this weekend.
Fixed!