SQS vs SNS : Detailed Comparison

CloudDeepDive
6 min readFeb 28, 2023
SNS vs SQS

Amazon Simple Queue Service (SQS) and Amazon Simple Notification Service (SNS) are two important messaging services provided by Amazon Web Services (AWS) that can be used to decouple the components of a cloud application. While both services can be used to send messages between different components, they serve different purposes and have different use cases. In this blog, we will compare the features and use cases of SQS and SNS to help you choose the right service for your application.

Amazon SQS:

SQS(Simple Queue Service)

Amazon SQS is a fully managed message queuing service that enables you to decouple and scale microservices, distributed systems, and serverless applications.

SQS is distributed queuing system. Messages are not pushed to receivers. Receivers have to poll SQS to receive messages. Messages can be stored in SQS for 1 min to Max 14 days.

Messages can’t be received by multiple receivers at the same time. Anyone receiver can receive a message, process and delete it. Other receivers do not receive the same message later. Polling inherently introduces some latency in message delivery in SQS, unlike SNS where messages are immediately pushed to subscribers.

Amazon SQS is a message queuing service that enables the reliable and scalable distribution of messages between different components of an application. SQS provides a fully managed message queuing service with a flexible API that supports both standard and FIFO (First-In-First-Out) queues.

Features of Amazon SQS:

  1. Message Queuing: SQS provides message queuing, which means that messages are stored in a queue until they are processed by a consumer. SQS ensures the reliable delivery of messages by storing them redundantly across multiple availability zones.
  2. Message Retention: SQS allows you to retain messages in a queue from one minute to 14 days. After the retention period expires, the messages are deleted automatically.
  3. Polling Mechanisms: SQS supports two polling mechanisms, short polling and long polling. Short polling returns immediately with either a message or an empty response. Long polling waits for a specified time for messages to arrive before returning a response.
  4. Message Size: SQS supports messages up to 256 KB in size. For larger messages, you can use S3 or SNS to send a message payload as a notification.
  5. Dead-Letter Queues: SQS provides the ability to set up a dead-letter queue for messages that cannot be processed. If a message cannot be processed after a specified number of attempts, it is moved to the dead-letter queue for further analysis.

Use Cases for Amazon SQS:

  1. Asynchronous Communication: SQS can be used for asynchronous communication between components of an application. When components are decoupled, they can communicate asynchronously, which enables each component to operate independently and can improve the overall performance and scalability of the application.
  2. Large Workloads: SQS is a highly scalable service that can handle any volume of messages. If your application needs to process a large number of messages, SQS can help you process them in a reliable and scalable way.
  3. Fault Tolerance: SQS can help improve the fault tolerance of your application. By storing messages redundantly across multiple availability zones (AZs), it can help prevent message loss in case of failure.
  4. Loose Coupling: SQS can help you achieve loose coupling between the components of your application. Loose coupling enables each component to evolve independently, making it easier to make changes to the application.

Amazon SNS:

SNS(Simple Notification Service)

Amazon SNS is a fast, flexible, fully managed push notification service that lets you send individual messages or to bulk messages to large numbers of recipients. Amazon SNS makes it simple and cost effective to send push notifications to mobile device users, email recipients or even send messages to other distributed services.

SNS is a distributed publish-subscribe system. Messages are pushed to subscribers as and when they are sent by publishers to SNS.

Amazon SNS is a fully managed pub/sub messaging service that enables the decoupling of components of a cloud application by allowing them to communicate asynchronously. SNS provides a simple and flexible API that allows you to send messages to multiple recipients or subscribers.

Features of Amazon SNS:

  1. Publish/Subscribe Model: SNS provides a publish/subscribe messaging model, which means that publishers send messages to a topic, and subscribers receive messages from that topic.
  2. Multiple Protocols: SNS supports multiple protocols, including HTTP/S, email, SMS, mobile push notifications, and Lambda functions.
  3. Fanout: SNS allows you to fan out messages to multiple recipients, which can improve the scalability and performance of your application.
  4. Message Filtering: SNS provides message filtering, which enables you to send messages only to subscribers that are interested in a particular topic or message attribute.

Use Cases for Amazon SNS:

  1. Notifications: SNS can be used to send notifications to multiple subscribers, such as email, SMS, mobile push notifications, and other messaging channels.
  2. Event-driven Architecture: SNS can be used as an event-driven architecture, where events are published to a topic and then processed by subscribers. This enables the decoupling of components and can help improve the scalability and performance of the application.
  3. Fanout: SNS allows you to fan out messages to multiple recipients, which can improve the scalability and performance of your application.
SNS fan out with SQS

4. Message Filtering: SNS provides message filtering, which enables you to send messages only to subscribers that are interested in a particular topic or message attribute.

Comparison between Amazon SQS and Amazon SNS:

  1. Messaging Model: SQS provides a message queuing service, while SNS provides a publish/subscribe messaging service.
  2. Message Retention: SQS retains messages for a specified period, while SNS does not retain messages.
  3. Protocols: SNS supports multiple protocols, while SQS supports only HTTP/S.
  4. Message Filtering: SNS provides message filtering, while SQS does not.
  5. Fanout: SNS allows you to fan out messages to multiple recipients, while SQS does not.

Use Cases:

  • SQS is best used for asynchronous communication between components, handling large workloads, achieving loose coupling, and improving fault tolerance.
  • SNS is best used for notifications, event-driven architecture, fanout, and message filtering.

Conclusion:

Amazon Simple Queue Service (SQS) and Amazon Simple Notification Service (SNS) are two powerful messaging services provided by AWS that can help decouple the components of a cloud application. While both services can be used to send messages between different components, they serve different purposes and have different use cases.

SQS is best used for asynchronous communication between components, handling large workloads, achieving loose coupling, and improving fault tolerance, while SNS is best used for notifications, event-driven architecture, fanout, and message filtering. By understanding the features and use cases of these services, you can choose the right service for your application and improve its performance, scalability, and reliability.

Thanks for reading!!! Let me know in the comment section if you want a detailed article to cover the SQS and SNS alone.

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