https://aws.amazon.com/premiumsupport/knowledge-center/aws-batch-requests-error/
https://aws.amazon.com/premiumsupport/knowledge-center/api-gateway-429-limit/
The main problem is that one client is generating a large number of PUT requests, resulting in increased errors. Because the clients are authenticated by API keys and the problematic traffic is concentrated among a small set of clients, API Gateway usage plans and throttling are a direct control mechanism to limit the request rate per client (or per API key). The API is noncritical and clients can tolerate retries, so returning throttling responses is acceptable as long as clients handle them correctly. The goal is to reduce visible customer-facing errors and protect the API from being overwhelmed by a single client.
API Gateway usage plans can set request throttling limits (rate and burst) per API key. When a client exceeds the configured throttle, API Gateway returns HTTP 429 (Too Many Requests). If the client application is designed to treat 429 as a normal, retryable condition rather than a fatal error, the user experience improves because the client can back off and retry instead of surfacing raw failures. This approach prevents one noisy client from degrading service for other users and reduces the overall error rate.
Option B addresses the root cause (excess requests from a particular client) by enforcing throttling at the API Gateway layer and improving client behavior when throttled.
Option A focuses on client-side retries and error handling but does not enforce fairness or prevent a single client from consuming disproportionate API capacity. Without throttling, the same client can continue to overload downstream Lambda and DynamoDB capacity and still cause errors for everyone.
Option C (API caching) does not help for PUT requests because PUT operations are writes and are generally not cacheable in a way that reduces write load. Caching is mainly beneficial for GET responses and read-heavy workloads.
Option D (reserved concurrency) can protect Lambda capacity for critical functions, but it can also cause throttling at the Lambda layer and does not directly address controlling the request rate per API key. It also does not fix the issue at the API front door where the noisy client should be managed.
Therefore, implementing API Gateway throttling via a usage plan and ensuring clients handle 429 responses properly is the best recommendation.
[References:AWS documentation on Amazon API Gateway usage plans and API key throttling, including rate and burst limits and 429 responses.AWS best practices for handling throttling responses with retries and backoff for improved client experience., , , ]
