When you exceed a daily limit (calls per day) the API will return an HTTP 429 error until the rate limit resets at 00 UTC.
When you exceed a per second limit (calls per second) the requests in excess of this limit will receive an HTTP 429 error from the API.
If you are hitting any of these limits we recommend either reducing call velocity, retrying requests that fail due to rate limiting, or changing your subscription to one that has higher limits.