A developer is trying to retrieve data over a REST API. The API server responds with an HTTP client error response code. After investigating the response the developer realizes the response has a…

Question

Options

• AAn appliance limited the rate of requests to the transport layer.
• BThe REST service is unreachable at the time of the REST request.
• CToo many requests were sent to the REST service in a given amount of time.
• DAn appliance limited the rate of requests to the application layer.

• A
  4% (1)
• C
  93% (26)
• D
  4% (1)

Explanation

The Retry-After response header is specifically associated with HTTP 429 Too Many Requests, a client-side error (4xx). It indicates the client has exceeded the API's rate limit - sending too many requests in a given time window. The server returns Retry-After to tell the client how long to wait before making another request. Option A and D are incorrect because rate limiting at the transport layer or by an appliance (e.g., a firewall) would typically not surface a Retry-After header in an HTTP response - that header comes from the application layer API server itself. Option B is incorrect because service unreachability would result in a 503 Service Unavailable (a server-side 5xx error), which can also use Retry-After, but the question states it is an HTTP client error (4xx), pointing directly to 429.

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