The first page of their documentation [0] mentions this:
> Opening a database > In your Deno program, you can get a reference to a KV database using Deno.openKv(). You may pass in an optional file system path to where you'd like to store your database, otherwise one will be created for you based on the current working directory of your script.
In fact, only the last page in the documentation speaks about KV on Deno Deploy.