Amazon SNS Topics ​

Amazon SNS Topics are named communication channels within the Simple Notification Service that serve as the central connection point between message publishers and subscribers. In email delivery systems, SNS Topics play a vital role in managing and distributing notifications about email events such as bounces, complaints, and deliveries as part of the Amazon SNS service.

What are Amazon SNS Topics? ​

An SNS Topic is a logical access point and communication channel in Amazon Simple Notification Service. It functions as an event router that receives messages from publishers and fans them out to all subscribed endpoints. For email operations, topics are the backbone of feedback processing systems, enabling real-time handling of important delivery events.

According to AWS documentation, a single SNS topic can support deliveries to millions of subscriptions (up to 12.5 million subscriptions per standard topic), making it suitable for high-volume email notification processing.

How SNS Topics Work ​

SNS Topics operate through a publish-subscribe architecture that enables one-to-many message distribution. When a topic receives a message, it immediately makes copies and distributes them to all subscribed endpoints. This fan-out pattern is fundamental to understanding how email event notifications work.

A key feature of SNS Topics is message filtering, which allows subscribers to receive only specific message types at the subscription level. In email systems, this means different processors can receive only the specific email events they're designed to handle, such as bounces or complaints, without needing to process all topic messages.

Topic Types and Characteristics ​

Amazon SNS offers two distinct topic types with different delivery characteristics:

Standard Topics – High-throughput, best-effort ordering, at-least-once delivery. These topics can handle very high message volumes (up to 30,000 messages per second in some regions) according to AWS documentation, making them ideal for most email notification scenarios.

FIFO (First-In-First-Out) Topics – Strict ordering, exactly-once delivery, lower throughput. These topics are useful when the precise sequence of email events matters, though they have significantly lower message processing limits than Standard Topics.

Core Benefits of SNS Topics ​

SNS Topics provide several fundamental benefits in message distribution systems:

The real-time message distribution enables immediate responses to delivery failures, bounces, or complaints, critical for maintaining sender reputation and campaign health.

Their scalable architecture handles varying message volumes without configuration changes, allowing systems to adapt automatically to traffic spikes and varying workloads.

The loose coupling principle means that publishers and subscribers can evolve independently, creating more flexible and maintainable system architectures.

Frequently Asked Questions About SNS Topics ​

How many subscribers can an SNS Topic have? ​

A single SNS Topic can support up to 12.5 million subscriptions across various endpoint types, according to AWS documentation.

Can SNS Topics guarantee message processing order? ​

Standard SNS Topics provide best-effort ordering but don't guarantee it. FIFO Topics ensure strict ordering with exactly-once processing guarantees, though with lower throughput.

How reliable is message delivery with SNS Topics? ​

SNS implements a "at-least-once" delivery model with automatic retries for failed deliveries. This design ensures high message durability even during temporary endpoint disruptions.

How can filtering improve email operations? ​

In SES email systems, SNS topic filtering allows distinct handling logic for hard bounces, soft bounces, complaints, and deliveries. For example, organizations can route hard bounces to immediate suppression list updates while sending soft bounces to a monitoring system for tracking transient failures.

Related Content ​

• Amazon SNS (Simple Notification Service)
• Amazon SNS Subscriptions
• Amazon SES (Simple Email Service)
• Email Bounces
• Email Complaints