SNS (Simple Notification Service)

• What if you want to send one message to many receivers?
• The "event publishers" only sends message to one SNS topic
• As many "event subscribers" as we want to listen to the SNS topic notifications
• Each subscriber to the topic will get all the messages
• Up to 12,500,000 subscriptions per topic, 100,000 topics limit

SNS integrates with a lot of AWS services

Publish

• Topic Publish (using the SDK)
  • Create a topic
  • Create a subscription (or many)
  • Publish to the topic
• Direct Publish (for mobile apps SDK)
  • Create a platform application
  • Create a platform endpoint
  • Publish to the platform endpoint
  • Works with Google GCM, Apple APNS, Amazon ADM…

Security

• Encryption:
  • In-flight encryption using HTTPS API
  • At-rest encryption using KMS keys
  • Client-side encryption if the client wants to perform encryption/decryption itself
• Access Controls: IAM policies to regulate access to the SNS API
• SNS Access Policies (similar to S3 bucket policies)
  • Useful for cross-account access to SNS topics
  • Useful for allowing other services ( S3…) to write to an SNS topic

SNS + SQS: Fan Out

• Push once in SNS, receive in all SQS queues that are subscribers
• Fully decoupled, no data loss
• SQS allows for: data persistence, delayed processing and retries of work
• Ability to add more SQS subscribers over time
• Make sure your SQS queue access policy allows for SNS to write
• Cross-Region Delivery: works with SQS Queues in other regions

SNS to Amazon S3 through Kinesis Data Firehose

• SNS can send to Kinesis and therefore we can have the following solutions architecture

FIFO (First in first out)topics

• Similar features as SQS FIFO:
  • Ordering by Message Group ID (all messages in the same group are ordered)
  • Deduplication using a Deduplication ID or Content Based Deduplication
• Can have SQS Standard and FIFO queues as subscribers
• Limited throughput (same throughput as SQS FIFO)

SNS Message Filtering

• JSON policy used to filter messages sent to SNS topic’s subscriptions
• If a subscription doesn’t have a filter policy, it receives every message