What is 'API throttling vs rate limiting' and when would you use each for a public API?

• A.Throttling and rate limiting are identical concepts with different names
• B.Throttling is for paid APIs; rate limiting is only for free tier APIs
• C.Rate limiting restricts the number of requests in a time window (100 requests/minute - exceeding returns 429). Throttling degrades service quality for excess requests rather than rejecting them (slow down responses, prioritize lower-load clients). Rate limiting protects backend resources by rejecting excess; throttling provides graceful degradation. Public APIs often use rate limiting for abuse prevention and throttling for fair resource distribution among legitimate users
• D.Rate limiting is enforced at the network layer; throttling is enforced at the application layer