Requests that go beyond the per-second limits associated with your plan will return with an "Rate Limited Second" error and a '429' error code.
"error": "Rate Limited Second"
You can implement a queue on your end or a retry logic, such that requests that return with this error are sent back again after a second.
If none of these options work for you, write to us with details around your implementation and we'll arrange a custom plan with higher RPS for you.