Amazon SNS: Part 1 – Introduction for Developers and Architects

By | February 5, 2024

Amazon SNS (Simple Notification Service) is a fully managed pub/sub messaging service from Amazon designed to provide highly scalable, flexible, and cost-effective communication between different components of an application. SNS is particularly adept at enabling real-time and event-driven architectures by broadcasting events to many subscribers, including serverless functions, email addresses, mobile devices, and more.

(This post was originally here, but I have moved it out to its own page and added more clarity)

(Also be sure to check out “Amazon SNS: Part 2 – When to use AWS SNS…”. Coming Soon).

Application Collaboration

SNS introduces a publish/subscribe communication model, simplifying and decoupling the interaction between producers and consumers of messages. Producers publish messages to topics, which are logical access points and communication channels. Subscribers (such as HTTP endpoints, Lambda functions, email addresses, mobile devices, etc.) receive messages published to the topics they subscribe to.

Message Lifecycle

  • Message Publication: Producers publish events to SNS topics without worrying about the subscribers’ details, ensuring a decoupled system architecture.
  • Topic Subscription: Subscribers subscribe to topics and receive messages as per their selected protocol (email, SMS, HTTP/S endpoints, etc.). SNS manages these subscriptions, ensuring events are delivered promptly and accurately.
  • Message Delivery: SNS ensures reliable and scalable delivery of messages to all subscribers, supporting multiple protocols and managing retries and message delivery status.

SNS Features and Benefits

  1. Multi-Protocol Support: SNS supports a range of protocols, enabling comprehensive and diverse communication strategies. across both application-to-application (A2A) endpoints (Amazon SQS, Amazon Kinesis Data Firehose, AWS Lambda, HTTPS) and application-to-person (A2P) endpoints (SMS, mobile push and email).
  2. High Throughput and Scalability: SNS standard topics support a nearly unlimited number of events per second. And millions of subscriptions (12.5 Million) per topic.
  3. Fan-Out Architecture: SNS supports the fan-out pattern, enabling a single published events to be delivered to millions of subscribers across different services, ensuring parallel and timely processing.
  4. Message Filtering: Subscribers can filter and receive only the events that meet specific criteria, optimizing event processing and reducing unnecessary network traffic.
  5. Integration with AWS Ecosystem: SNS integrates seamlessly with other AWS services, allowing you to build complex, responsive, and reliable applications. This integration facilitates diverse workflows and event-driven architectures.
  6. Robust Security and Access Management: With comprehensive IAM policies and encryption options, SNS ensures secure message handling and controlled access to topics, maintaining communication integrity and data confidentiality.
  7. Durable Event Delivery: SNS makes best effort to deliver events through a multi-phased delivery policy. It includes immediate retries, and with jitter multiple delayed retries, and exponential backoff. Depending on the subscriber type, SNS retries up to 50 times within 6 hours for standard endpoints and over 100,000 times across 23 days for Amazon-managed services. Additionally, subscribers can specify an SNS Dead Letter Queue using Amazon SQS for undeliverable messages.
  8. Strict Message Ordering: Integrating Amazon SNS FIFO topics with SQS FIFO queues ensures precise event ordering and deduplication, which is essential for distributed applications needing real-time data consistency. While subscribing SQS standard queues to SNS FIFO topics provides approximate ordering and guaranteed delivery. However, the ordering comes at a cost. Therefore SNS FIFO has limitations: it supports only up to 300 events per second or 10 MB per second, with a maximum of 100 SQS queues per topic and 1000 per AWS account, compared to 12.5 million subscribers for standard topics.
  9. No Event Retention/Persistence: With SNS, there’s no event persistence; if a subscriber is unavailable or fails during processing, the message is not delivered and is lost.


Amazon SNS is a vital component within the AWS ecosystem, marked by its exceptional flexibility, scalability, and reliability. It’s crafted to facilitate efficient, secure, and versatile messaging, empowering your architecture to respond swiftly and effectively in a rapidly changing cloud environment. The extensive feature set of SNS strengthens your system’s communication capabilities, ensuring it remains dynamic, responsive, and adaptable.

However, it’s crucial to consider and mitigate potential challenges associated with SNS to utilize its benefits fully:

  1. Message Ordering: SNS does not inherently guarantee the order of message delivery when using protocols other than FIFO queues. Applications requiring strict message sequencing might need additional handling or architecture considerations.
  2. Message Retention: If a subscriber is not actively subscribed to a topic when a event arrives, the event won’t be delivered. This can lead to unsynchronized processes and potential data integrity issues, as services may miss crucial updates.
  3. Integration Complexity: Depending on the use case, integrating SNS with multiple subscriber types and managing diverse message formats can introduce complexity. Proper planning and management are essential to ensure seamless communication flows.

In conclusion, Amazon SNS provides a powerful framework for pub/sub messaging, enabling a loosely coupled and highly adaptable communication environment. By thoughtfully addressing aspects like message ordering and cost management, you can maximize the potential of SNS, enhancing the responsiveness, agility, and overall effectiveness of your system’s messaging infrastructure.

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