SQS · Simple Queue Service

Outcome

• Queues & DLQsQueue Basics: Send, Receive, Delete
  • Create a standard queue with the right visibility timeout and retention settings
  • Send single messages, batches, and messages with attributes
  • Explain why receive does not delete, and what happens if you forget to delete
  • Read ApproximateNumberOfMessagesNotVisible and know what it means
  • Handle an expired receipt handle error and explain how to prevent it
• Queues & DLQsVisibility Timeout + Polling Mechanics
  • Explain the difference between short polling and long polling and when to use each
  • Set ReceiveMessageWaitTimeSeconds=20 at the queue level
  • Use change-message-visibility as a heartbeat for slow consumers
  • Write a correct consumer loop: receive → process → delete on success, no-op on failure
  • Explain what at-least-once delivery means for consumer idempotency
• Queues & DLQsDead Letter Queues + Redrive
  • Create a DLQ and attach it with a redrive policy
  • Trigger DLQ routing by failing messages N times and observe ApproximateReceiveCount
  • Use start-message-move-task to redrive messages back without a custom Lambda
  • Explain the DLQ retention trap and why DLQ retention must be >= source retention
• Queues & DLQsFIFO Queues + Message Groups + Deduplication
  • Create a FIFO queue with content-based deduplication and a FIFO DLQ
  • Send messages with MessageGroupId and explain what it controls
  • Observe strict ordering within a group and independent delivery across groups
  • Demonstrate head-of-line blocking by holding a message in-flight
  • Verify deduplication by sending the same body twice and confirming queue depth = 1
• Queues & DLQsObservability: CloudWatch Metrics + Alarms
  • Name the six SQS CloudWatch metrics and what each measures
  • Explain why ApproximateAgeOfOldestMessage is more actionable than queue depth alone
  • Create DLQ, message age, and queue depth alarms with correct thresholds and treatMissingData
  • Diagnose slow-consumer vs stopped-consumer using Visible and NotVisible metrics
  • Explain why SQS metrics have 5-minute resolution and what that means for alarm response time