SNS · Simple Notification Service

Outcome

• Topics & Fan-outTopic Basics: Create, Subscribe, Publish
  • Create a standard SNS topic and explain push vs pull (SNS vs SQS)
  • Subscribe an email endpoint and explain why confirmation is required
  • Publish a message and describe the SNS envelope structure
  • Use publish-batch and check for per-entry failures
  • Explain what MessageId represents at the SNS level
• Topics & Fan-outFan-Out: SNS → Multiple SQS Queues
  • Create the SNS→SQS fan-out pattern with correct access policies
  • Explain why SQS requires an explicit sqs:SendMessage allow from SNS
  • Enable raw message delivery and explain when not to use it
  • Identify silent delivery failure (missing SQS policy) and how to detect it
• Topics & Fan-outMessage Filtering
  • Write a filter policy for exact string, prefix, and numeric matching
  • Explain what happens to a message that matches no subscriber
  • Name the CloudWatch metric that tracks filtered-out messages
  • Remove a filter policy and explain the {} vs absent distinction
• Topics & Fan-outDead Letter Queues + Retry Behavior
  • Distinguish SNS delivery DLQ from SQS consumer DLQ, two different failure modes
  • Configure a redrive policy on an SNS subscription
  • Trigger a delivery failure and verify the message lands in the SNS delivery DLQ
  • Explain SNS retry behavior per endpoint type (SQS vs HTTP vs Lambda vs email)
• Topics & Fan-outFIFO Topics
  • Create an SNS FIFO topic and explain the subscriber type constraint
  • Publish with MessageGroupId and verify ordering end-to-end
  • Demonstrate content-based deduplication at the SNS layer
  • Explain the throughput limit and when FIFO is the wrong choice
• Topics & Fan-outObservability: CloudWatch Metrics + Alarms
  • Name the five key SNS CloudWatch metrics and what each indicates
  • Create a delivery failure alarm with correct TreatMissingData setting
  • Build a metric math alarm for high filter rate
  • Use the five-metric decision tree to diagnose a silent message loss