Rate limit
How many requests a read key may make, and what happens over the limit.
Currently 60 requests per 60 seconds per key - a read key has its own budget, shared with nothing else. Over the limit the API answers 429 with Retry-After: 60 and the usual error body, {"error": "Too many requests with this read key. Wait 60 seconds, then retry.", "code": "rate_limited"}. A caller far beyond the limit can be stopped earlier by the edge firewall with a bare 429 - no body, no Retry-After: wait 60 seconds just the same.
Retries
Section titled “Retries”429: wait the seconds Retry-After names (60), then retry. Requests are counted per key in 60-second windows. 5xx: retry with exponential backoff, starting at 1 second and capped at 30 seconds. 400, 401, 403, 404: never retry - the same request gets the same answer.