limit
The limit method is the heart of the Ratelimit algorithm.
req parameter which can contain either a
geo or a rate field. geo field is passed to the analytics but is not in use currenlty. The rate field determines
the amount of tokens/requests to subtract from the state of the algorithm with regards to the provided identifier.
blockUntilReady
In case you don’t want to reject a request immediately but wait until it can be
processed, we also provide
limit method and takes an identifier and returns the
same response. However if the current limit has already been exceeded, it will
automatically wait until the next window starts and will try again. Setting the
timeout parameter (in milliseconds) will cause the returned Promise to resolve
in a finite amount of time.
In Cloudflare, 
For more information, check:
https://developers.cloudflare.com/workers/runtime-apis/web-standards
blockUntilReady will not work as intended due to Date.now() not behaving the same as in Node environments.For more information, check:
https://developers.cloudflare.com/workers/runtime-apis/web-standards