CONCEPT Cited by 1 source

Cross-region fan-out

Definition

Cross-region fan-out is the distribution of a single event to processing infrastructure in multiple AWS (or cloud) regions simultaneously. The event originates in one region and is delivered — typically via messaging infrastructure (SNS subscriptions, EventBridge rules, or Kafka MirrorMaker) — to consumers in two or more target regions.

The key distinction from replication is intent: fan-out delivers the event for processing (one consumer will act on it), whereas replication delivers data for durability (all replicas store it).

Why it matters

Without cross-region fan-out, multi-region architectures must choose between:

1. Single-region processing — fast but creates a single point of failure.
2. Client-side multi-publish — complex, error-prone, and couples the publisher to the topology.
3. Infrastructure-level fan-out — clean separation of concerns; the publisher doesn't know how many regions consume.

Option 3 (infrastructure fan-out) is the canonical approach in AWS architectures using SNS cross-region subscriptions or EventBridge cross-region rules.

Seen in

• sources/2026-07-22-aws-building-multi-region-resiliency-for-cloudformation-custom-resources — SNS topics in customer regions fan out CloudFormation lifecycle events to SQS queues in both us-east-1 and us-west-2 simultaneously (AWS Architecture Blog, 2026-07-22).