Limits
What one key may do in a minute.
Counted per key, not per address. A whole data centre can sit behind one address, and one key may call from anywhere — the key is the only identity that is right in both directions.
Calls in a burst
240
Calls per minute after that
120
Answer when exceeded
429 · Retry-After
These figures come from the setting this installation actually uses.
A bucket, not a window.
A counter that resets every minute is twice as generous at its own boundary as it looks. A bucket that refills steadily has no such edge: you may be fast at the start and are then throttled evenly.
When it gets tight.
Wait exactly the time named rather than retrying at once; pull larger pages instead of more pages; and split a loud integration across two keys — the logs then also say which half was loud.