AWS SNS Amazon Simple Notification Service (SNS) is a fully managed pub/sub messaging service for application-to-application (A2A) and application-to-person (A2P) communication. Table of Contents Core Concepts Common Patterns CLI Reference Best Practices Troubleshooting References Core Concepts Topics Named channels for publishing messages. Publishers send to topics, subscribers receive from topics. Topic Types Type Description Use Case Standard Best-effort ordering, at-least-once Most use cases FIFO Strict ordering, exactly-once Order-sensitive Subscription Protocols Protocol Description Lambda Invoke Lambda function SQS Send to SQS queue HTTP/HTTPS POST to endpoint Email Send email SMS Send text message Application Mobile push notification Message Filtering Route messages to specific subscribers based on message attributes. Common Patterns Create Topic and Subscribe AWS CLI:

Create standard topic

aws sns create-topic --name my-topic

Create FIFO topic

aws sns create-topic \ --name my-topic.fifo \ --attributes FifoTopic = true

Subscribe Lambda

aws sns subscribe \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --protocol lambda \ --notification-endpoint arn:aws:lambda:us-east-1:123456789012:function:my-function

Subscribe SQS

aws sns subscribe \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --protocol sqs \ --notification-endpoint arn:aws:sqs:us-east-1:123456789012:my-queue

Subscribe email

aws sns subscribe \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --protocol email \ --notification-endpoint user@example.com boto3: import boto3 sns = boto3 . client ( 'sns' )

Create topic

response

sns . create_topic ( Name = 'my-topic' ) topic_arn = response [ 'TopicArn' ]

Subscribe Lambda

sns . subscribe ( TopicArn = topic_arn , Protocol = 'lambda' , Endpoint = 'arn:aws:lambda:us-east-1:123456789012:function:my-function' )

Subscribe SQS with filter

sns . subscribe ( TopicArn = topic_arn , Protocol = 'sqs' , Endpoint = 'arn:aws:sqs:us-east-1:123456789012:order-queue' , Attributes = { 'FilterPolicy' : '{"event_type": ["order_created", "order_updated"]}' } ) Publish Messages import boto3 import json sns = boto3 . client ( 'sns' ) topic_arn = 'arn:aws:sns:us-east-1:123456789012:my-topic'

Simple publish

sns . publish ( TopicArn = topic_arn , Message = 'Hello, World!' , Subject = 'Notification' )

Publish with attributes (for filtering)

sns . publish ( TopicArn = topic_arn , Message = json . dumps ( { 'order_id' : '12345' , 'status' : 'created' } ) , MessageAttributes = { 'event_type' : { 'DataType' : 'String' , 'StringValue' : 'order_created' } , 'priority' : { 'DataType' : 'Number' , 'StringValue' : '1' } } )

Publish to FIFO topic

sns . publish ( TopicArn = 'arn:aws:sns:us-east-1:123456789012:my-topic.fifo' , Message = json . dumps ( { 'order_id' : '12345' } ) , MessageGroupId = 'order-12345' , MessageDeduplicationId = 'unique-id' ) Message Filtering

Add filter policy to subscription

aws sns set-subscription-attributes \ --subscription-arn arn:aws:sns:us-east-1:123456789012:my-topic:abc123 \ --attribute-name FilterPolicy \ --attribute-value '{ "event_type": ["order_created"], "priority": [{"numeric": [">=", 1]}] }' Filter policy examples: // Exact match { "event_type" : [ "order_created" , "order_updated" ] } // Prefix match { "customer_id" : [ { "prefix" : "PREMIUM-" } ] } // Numeric comparison { "price" : [ { "numeric" : [ ">=" , 100 , "<=" , 500 ] } ] } // Exists check { "customer_id" : [ { "exists" : true } ] } // Anything but { "event_type" : [ { "anything-but" : [ "deleted" ] } ] } // Combined { "event_type" : [ "order_created" ] , "region" : [ "us-east" , "us-west" ] , "priority" : [ { "numeric" : [ ">=" , 1 ] } ] } Fan-Out Pattern (SNS to Multiple SQS) import boto3 import json sns = boto3 . client ( 'sns' ) sqs = boto3 . client ( 'sqs' )

Create topic

topic

sns . create_topic ( Name = 'orders-topic' ) topic_arn = topic [ 'TopicArn' ]

Create queues for different processors

queues

{ 'analytics' : sqs . create_queue ( QueueName = 'order-analytics' ) [ 'QueueUrl' ] , 'fulfillment' : sqs . create_queue ( QueueName = 'order-fulfillment' ) [ 'QueueUrl' ] , 'notification' : sqs . create_queue ( QueueName = 'order-notification' ) [ 'QueueUrl' ] }

Subscribe each queue

for name , queue_url in queues . items ( ) : queue_arn = sqs . get_queue_attributes ( QueueUrl = queue_url , AttributeNames = [ 'QueueArn' ] ) [ 'Attributes' ] [ 'QueueArn' ] sns . subscribe ( TopicArn = topic_arn , Protocol = 'sqs' , Endpoint = queue_arn )

One publish reaches all queues

sns . publish ( TopicArn = topic_arn , Message = json . dumps ( { 'order_id' : '12345' , 'total' : 99.99 } ) ) Lambda Permission for SNS aws lambda add-permission \ --function-name my-function \ --statement-id sns-trigger \ --action lambda:InvokeFunction \ --principal sns.amazonaws.com \ --source-arn arn:aws:sns:us-east-1:123456789012:my-topic CLI Reference Topic Management Command Description aws sns create-topic Create topic aws sns delete-topic Delete topic aws sns list-topics List topics aws sns get-topic-attributes Get topic settings aws sns set-topic-attributes Update topic settings Subscriptions Command Description aws sns subscribe Create subscription aws sns unsubscribe Remove subscription aws sns list-subscriptions List all subscriptions aws sns list-subscriptions-by-topic List topic subscriptions aws sns confirm-subscription Confirm pending subscription Publishing Command Description aws sns publish Publish message Best Practices Reliability Use SQS for durability — SNS is push-based, SQS queues messages Implement retries for HTTP/HTTPS endpoints Configure DLQ for failed deliveries Use FIFO topics for ordering requirements Security Use topic policies to control access Enable encryption with SSE Use VPC endpoints for private access

Enable SSE

aws sns set-topic-attributes \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --attribute-name KmsMasterKeyId \ --attribute-value alias/my-key Cost Optimization Use message filtering to reduce unnecessary deliveries Batch operations where possible Monitor and clean up unused topics/subscriptions Message Design Keep messages small (256 KB limit) Use message attributes for routing Include correlation IDs for tracing Troubleshooting Subscription Not Receiving Messages Check: Subscription is confirmed (not pending) Filter policy matches message attributes Target permissions (Lambda, SQS)

Check subscription status

aws sns list-subscriptions-by-topic \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic

Check subscription attributes

aws sns get-subscription-attributes \ --subscription-arn arn:aws:sns:us-east-1:123456789012:my-topic:abc123 HTTP Endpoint Not Working Debug:

Check delivery status logging

aws sns set-topic-attributes \ --topic-arn arn:aws:sns:us-east-1:123456789012:my-topic \ --attribute-name DeliveryPolicy \ --attribute-value '{ "http": { "defaultHealthyRetryPolicy": { "minDelayTarget": 20, "maxDelayTarget": 20, "numRetries": 3, "numMaxDelayRetries": 0, "numNoDelayRetries": 0, "numMinDelayRetries": 0, "backoffFunction": "linear" } } }' Messages Not Matching Filter Verify: Message attributes are set (not in body) Attribute types match (String vs Number) Filter policy syntax is correct

Correct: attributes must be message attributes

sns . publish ( TopicArn = topic_arn , Message = 'body content' , MessageAttributes = { 'event_type' : { 'DataType' : 'String' , 'StringValue' : 'order_created'

This is filtered

} } )

Wrong: this won't be filtered

sns . publish ( TopicArn = topic_arn , Message = json . dumps ( { 'event_type' : 'order_created' } )

Not filtered

) SQS Not Receiving from SNS Check SQS queue policy: { "Version" : "2012-10-17" , "Statement" : [ { "Effect" : "Allow" , "Principal" : { "Service" : "sns.amazonaws.com" } , "Action" : "sqs:SendMessage" , "Resource" : "arn:aws:sqs:us-east-1:123456789012:my-queue" , "Condition" : { "ArnEquals" : { "aws:SourceArn" : "arn:aws:sns:us-east-1:123456789012:my-topic" } } } ] } References SNS Developer Guide SNS API Reference SNS CLI Reference boto3 SNS