A company is running a popular mobile game. The backend uses Amazon API Gateway and AWS Lambda. During special events, traffic spikes from 1,000 to 50,000 requests per second within minutes. Users are experiencing 502 Bad Gateway errors during these spikes. The Lambda functions connect to an Amazon RDS Proxy, which connects to an Aurora PostgreSQL database. What is the MOST likely cause of the errors and how should it be resolved?

Answer options:

Lambda is hitting its account-level concurrency limit. Request a quota increase for Lambda concurrent executions.

API Gateway is throttling the requests. Increase the API Gateway default rate limit.

RDS Proxy is running out of connections. Increase the MaxConnections setting on the RDS Proxy.

Lambda cold starts are causing timeouts. Enable Provisioned Concurrency for the Lambda functions.

How to approach this question

Identify the default AWS service limits that would be breached by a 50x traffic spike.

Full Answer

A.Lambda is hitting its account-level concurrency limit. Request a quota increase for Lambda concurrent executions.✓ Correct

Lambda is hitting its account-level concurrency limit. Request a quota increase for Lambda concurrent executions.

AWS Lambda has a default account-level concurrent execution limit of 1,000 per region. When traffic spikes to 50,000 requests per second, Lambda will throttle the requests. When API Gateway cannot invoke the Lambda function due to throttling, it returns a 502 Bad Gateway or 503 Service Unavailable error. You must request a quota increase from AWS Support.

Common mistakes

Confusing API Gateway throttling (429) with Lambda integration failures (502).

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