A request over the limit returns
429 RATE_LIMIT_EXCEEDED with a Retry-After header in seconds, and the event is logged as a security incident.
Partner keys also carry per-partner limits set at provisioning (rate_limit_per_minute, bulk_rate_limit_per_minute), which a Centsless administrator can raise for a pilot that needs more. If a POS platform expects sustained volume above the default, say so when requesting the pilot.
Registered locations keep the transaction path free of geocoding, so the limit is the only per-request cost a POS integration pays. Mobile overrides geocode on the request and count the same as any other request.