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You are a solutions architect working for an online retailer. Your online website uses REST API calls via API Gateway and Lambda from your Angular SPA front-end to interact with your DynamoDB data store. Your DynamoDB tables are used for customer preferences, account, and product information. When your web traffic spikes, some requests return a 429 error response. What might be the reason your requests are returning a 429 response

A. Your Lambda function has exceeded the concurrency limit

B. DynamoDB concurrency limit has been exceeded

C. Your Angular service failed to connect to your API Gateway REST endpoint

D. Your Angular service cannot handle the volume spike

E. Your API Gateway has exceeded the steady-state request rate and burst limits

1 Answer

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A. Your Lambda function has exceeded the concurrency limit

E. Your API Gateway has exceeded the steady-state request rate and burst limits

Answer: A & E

Explanation

Option A is correct. When your traffic spikes, your Lambda function can exceed the limit set on the number of concurrent instances that can be run (burst concurrency limit in the US: 3,000).

Option B is incorrect. When your table exceeds its provisioned throughput DynamoDB will return a 400 error to the requesting service, in this case, API Gateway. This will not result in the propagation of a 429 error response (too many requests) back to the Angular SPA service.

Option C is incorrect. If your Angular service fails to connect to your API Gateway REST endpoint your code will not generate a 429 error response (too many requests).

Option D is incorrect. Since your Angular SPA code runs in the individual user’s web browser, this option makes no sense.

Option E is correct. When your API Gateway request volume reaches the steady-state request rate and bursting limit, API Gateway throttles your requests to protect your back-end services. When these requests are throttled, API Gateway returns a 429 error response (too many requests).

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