AWS SQS vs SNS vs EventBridge

• AWS provides multiple messaging and event-driven services for decoupling application components.
• SQS is a message queue for point-to-point communication, SNS is a pub/sub notification service, and EventBridge is a serverless event bus for event-driven architectures.
• These services are often used together but serve different purposes.

SQS vs SNS vs EventBridge Comparison

Amazon SQS – Simple Queue Service

• Fully managed message queue for decoupling producers from consumers.
• Standard Queue – at-least-once delivery, best-effort ordering, unlimited throughput.
• FIFO Queue – exactly-once processing, strict ordering, up to 3,000 msg/sec with batching.
• Messages are retained up to 14 days – acts as a buffer for traffic spikes.
• Supports visibility timeout to prevent multiple consumers processing the same message.
• Supports long polling to reduce empty receives and costs.
• Dead Letter Queue (DLQ) for messages that fail processing after max retries.
• Integrates natively with Lambda (event source mapping) for serverless processing.

Amazon SNS – Simple Notification Service

• Fully managed pub/sub service for fan-out messaging to multiple subscribers.
• A single message published to a topic is delivered to all subscribers simultaneously.
• Supports multiple protocols – SQS, Lambda, HTTP/S, Email, SMS, Kinesis Data Firehose, mobile push.
• Message filtering – subscribers can set filter policies on message attributes to receive only relevant messages.
• FIFO topics – strict ordering and deduplication when paired with SQS FIFO queues.
• Fan-out pattern – SNS + multiple SQS queues for parallel processing of the same event.
• Supports message encryption (SSE-KMS) and cross-account subscriptions.

Amazon EventBridge

• Serverless event bus for building event-driven architectures at scale.
• Receives events from 90+ AWS services automatically (no configuration needed).
• Content-based filtering with event patterns – filter on any field in the event JSON body.
• Routes events to 200+ AWS service targets including Lambda, Step Functions, API Gateway, SQS, SNS.
• Schema Registry – automatically discovers and stores event schemas for code generation.
• Event Archive and Replay – store events indefinitely and replay them for debugging or reprocessing.
• EventBridge Scheduler – create one-time or recurring schedules (replaces CloudWatch Events cron).
• EventBridge Pipes – point-to-point integration between sources and targets with filtering, enrichment, and transformation.
• SaaS partner integrations – receive events from Zendesk, Datadog, Auth0, Shopify, etc.
• Global endpoints – automatic failover to a secondary region for high availability.

When to Choose Which

• Choose SQS – Decouple a producer from a single consumer, buffer traffic spikes, guarantee message processing with retries, maintain message ordering (FIFO).
• Choose SNS – Fan-out a message to multiple subscribers simultaneously, send notifications (email/SMS), simple pub/sub without complex routing.
• Choose EventBridge – React to AWS service events, route events based on content to different targets, integrate with SaaS applications, need schema discovery, event replay, or scheduling.
• Combine SNS + SQS – Fan-out pattern where each subscriber needs independent processing with buffering and retry.
• Combine EventBridge + SQS – Route events to SQS for buffered, reliable processing with backpressure handling.

AWS Certification Exam Practice Questions

1. A company needs to process orders where each order must be processed exactly once and in the order received. Which service and configuration is most appropriate?
   1. SNS Standard topic
   2. SQS FIFO queue
   3. EventBridge with ordering
   4. SQS Standard queue
2. An application needs to fan out a single event to three different microservices for parallel processing, each requiring independent retry logic. Which architecture is recommended?
   1. EventBridge with three targets
   2. SQS with three consumers
   3. SNS topic with three SQS queue subscriptions
   4. Three separate SQS queues with direct publishing
3. A team needs to automatically trigger a Lambda function whenever an S3 object is created, an EC2 instance changes state, or a CodePipeline deployment fails. Which service requires the least configuration?
   1. SNS with S3 event notifications
   2. SQS with CloudWatch Events
   3. EventBridge (receives AWS events automatically)
   4. Lambda with direct triggers
4. A SaaS application needs to react to events from Shopify and route them to different Lambda functions based on the event type (order_created vs order_cancelled). Which service is best suited?
   1. SNS with message filtering
   2. SQS with message attributes
   3. EventBridge with event pattern rules
   4. API Gateway with Lambda
5. After a production incident, a team needs to replay all events from the past 7 days to reprocess failed orders. Which service supports this natively?
   1. SQS (messages already consumed)
   2. SNS (no retention)
   3. EventBridge (Archive and Replay)
   4. Kinesis Data Streams

Related Posts

• AWS Simple Queue Service – SQS
• AWS Simple Notification Service – SNS
• AWS Kinesis Data Streams vs Kinesis Firehose
• AWS Certified Solutions Architect – Associate Exam Learning Path

References

Amazon SQS Developer Guide

Amazon SNS Developer Guide

Amazon EventBridge User Guide