Every key gets the same limit: 2 requests/second sustained, burst 10. Go over it and you get 429 with a Retry-After header (seconds to wait). Separately, all API traffic shares one global upstream reserve that protects capacity for ThreadSnoop's own discovery pipeline — if that shared pool is briefly exhausted you also get 429, but with an x-ratelimit-scope: global header so you can tell it apart from your own per-key limit. Neither case charges a credit. See Errors for the full list of status codes.