Which response would NOT be returned when an application is currently rate limited?

When an application is currently rate limited, the appropriate response indicates that the client has exceeded the allotted usage. One common way to convey this is through the HTTP response code 429, which specifically means "Too Many Requests." This status code informs the client that they must wait before making additional requests.

In a rate-limited response, you might also include a "retry-after" header. This header communicates how long the client should wait before sending another request, making this information crucial for managing request timing and adherence to rate limits. This means options that suggest the presence of such headers or the specific 429 code directly align with expected behavior during rate limiting.

While a 500 HTTP response code represents a server error indicating something went wrong on the server-side, it does not specifically relate to rate limiting. Therefore, an application that is rate limited will not return a 500 status code, as that code is reserved for different circumstances where the server itself has encountered an issue rather than the client exceeding allowed usage.

The other options, particularly those that involve the "retry-after" header and response code 429, are indeed correct and expected when an application is rate limited.