نمط التوزيع المتشعب باستخدام SNS

Fan-out means a single event is delivered to many subscribers at once, each processing it independently and in parallel.

Calling each downstream function from your producer tightly couples them. Adding a consumer means changing the producer. Fan-out decouples this.

Amazon SNS is a pub/sub topic. Publishers send a message once; SNS delivers a copy to every subscriber, including multiple Lambdas.

The producer publishes to the topic ARN. It does not know or care who is subscribed.

Each subscribed Lambda receives the message wrapped in an SNS records envelope.

Each consumer parses the message from the record and does its own job: one emails a receipt, another updates inventory.

For reliability, subscribe SQS queues to the topic and let Lambda poll the queues. This buffers spikes and gives each consumer its own retry and DLQ.

SNS filter policies let a subscriber receive only messages matching attributes, so not every consumer processes every event.

SNS is simple, high-throughput pub/sub. EventBridge adds richer routing, schemas, and many SaaS sources. Choose SNS for raw fan-out, EventBridge for complex routing.

Standard SNS topics do not guarantee order or exactly-once delivery. Use SNS FIFO topics when ordering and deduplication matter.

Because a message may be delivered more than once, each consumer should be idempotent so duplicates do not cause double effects.

You learned the fan-out pattern: publish once to SNS, deliver to many parallel consumers, add SQS for durability, filter messages, and keep consumers idempotent.