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A serverless app needs to fan out a single event to multiple downstream Lambda functions, each processing it independently. Which pattern is RECOMMENDED?
ASend each downstream system a separate HTTP POST from the producer with manual retries
BWrite the event to a single SQS queue and let all consumers compete for it
CStore the event in Amazon Glacier and let downstreams poll for it
DPublish the event to an SNS topic, with each downstream Lambda function as a subscriber
Answer & Solution
Correct answer: D. Publish the event to an SNS topic, with each downstream Lambda function as a subscriber
SNS pub/sub fan-out delivers one event to many subscribers (Lambdas, SQS queues, etc.) — purpose-built for this case. A single SQS queue produces competitive consumption (one wins). HTTP fan-out reinvents pub/sub. Glacier isn't an event bus.
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