SQS vs SNS vs EventBridge
SQS is a polling-based queue for one-to-one delivery. SNS is a push-based pub/sub service for one-to-many fan-out. EventBridge is an event bus that flexibly routes events to multiple targets based on rules.
| Aspect | Amazon SQS | Amazon SNS | Amazon EventBridge |
|---|---|---|---|
| Communication model | Polling-based queue (one-to-one) | Push-based pub/sub (fan-out) | Event bus (rule-based routing) |
| Message retention | Retained in queue up to 14 days | Standard has no built-in replay; FIFO supports archive/replay for up to 365 days | Not retained, routed immediately (archive/replay available) |
| Delivery target | Polling consumers (Standard is at-least-once, so processing must be idempotent) | Multiple subscribers simultaneously | Multiple targets based on rules |
| Ordering | None by default; FIFO queue guarantees order | None by default; FIFO topic guarantees order | Not guaranteed |
| Typical use | Decoupling async processing, worker queues | Fan-out delivery, notifications (email/SMS/push) | SaaS integration, event-driven service coordination, scheduling |
How to Choose
Use SQS to queue work for asynchronous consumers. Standard queues provide at-least-once delivery, so consumers must be idempotent and tolerate duplicates. Use SNS to fan out one event to multiple subscribers at once. Use EventBridge for SaaS partner integration, complex event pattern routing, or scheduled execution. Many architectures combine SNS → SQS fan-out, giving each subscriber its own queue for retry resilience.
Exam Points
- SAA frequently tests "process an S3 event with multiple Lambdas" → SNS fan-out vs "queue orders for sequential worker processing" → SQS
- The SNS + SQS fan-out pattern for loose coupling is a recurring architecture question
- DOP/SAP cover EventBridge scheduling and SaaS integration via partner event sources
Related Service Guides
References
Last updated: 2026-09-06
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