SNS - SQS

Feature	SNS	SQS	SNS + SQS
Durable delivery	❌ No storage	✅ Yes — persisted until consumed	✅ Yes — SQS provides durability
Retry on failure	⚠️ Limited retries	✅ Yes — visibility + DLQ support	✅ Yes — full retry logic via SQS
Consumer down? Buffer anyway?	❌ No — message may be lost	✅ Yes — stays in queue	✅ Yes — buffered in SQS
Multiple consumers w/ isolation	⚠️ Tricky to isolate	⚠️ Competing consumers only	✅ Each queue is isolated
Replayable delivery	❌ Not supported	❌ Not after consumption	✅ Can reprocess within retention
At-least-once delivery	❗ Best effort only	✅ Guaranteed	✅ Guaranteed via SQS

Bonus

Tie SNS -> SQS to have more Kafka like delivery pipeline.