An application built with Amazon API Gateway, AWS Lambda, and Amazon DynamoDB is returning increasing numbers of errors for PUT requests. Most PUT requests come from a small set of clients authenticated with API keys, and one client is generating many of the requests. The API is noncritical and clients can retry failed requests, but visible errors are damaging customer perception. What should you recommend to improve customer experience?

The problem describes a scenario where a few clients, particularly one, are overwhelming the API with PUT requests, leading to errors. Throttling with an API Gateway usage plan is the most direct and effective solution. It allows you to set limits on request rates and bursts per API key, preventing a single client from monopolizing resources and causing errors for others. This protects the backend (Lambda and DynamoDB) from overload. Clients receiving 429 errors can then implement retry logic, improving overall customer experience by gracefully handling temporary rate limits. Adding retry logic in the client application alone (option 1) is good practice but doesn't solve the root cause of the API being overwhelmed. Enabling API caching (option 3) is for GET requests and won't help with PUT requests. Setting reserved concurrency on Lambda (option 4) might prevent Lambda from being throttled but doesn't address the upstream issue of a single client overwhelming the API Gateway or the downstream DynamoDB.