SNS (Simple Notification Service) endpoints

SNS endpoints allow you to send webhook events to AWS SNS topics instead of HTTP endpoints.

This is useful for publishing events to notification topics without your customers having to set up any listener endpoint or write any glue code. SNS endpoints are ideal for:

• Fan-out messaging: Deliver events to multiple subscribers
• Multi-protocol delivery: Support email, SMS, HTTP, and other protocols
• Reliability: Leverage SNS's durability and retry mechanisms
• Scalability: Handle high-throughput event publishing

Configuration

Create an SNS endpoint by providing your SNS topic ARN and AWS credentials. Events will be published to your topic as individual messages.

curl -X 'POST' \
  'https://api.eu.svix.com/api/v1/stream/{your_sink_id}/sink' \
  -H 'Authorization: Bearer AUTH_TOKEN' \
  -H 'Accept: application/json' \
  -H 'Content-Type: application/json' \
  -d '{
    "config": {
      "topicArn": "arn:aws:sns:us-east-1:123456789012:my-topic",
      "region": "us-east-1",
      "accessKeyId": "xxx",
      "secretAccessKey": "xxx"
    },
    "type": "sns"
  }'

Transformation

SNS endpoints use transformations to format events for the target topic. Here's the transformation function for SNS:

/**
 * @param input - The input object
 * @param input.events - The array of events in the batch. The number of events in the batch is capped by the Sink's batch size.
 * @param input.events[].payload - The message payload (string or JSON).
 * @param input.events[].eventType - The message event type (string).
 *
 * @returns Object containing the response.
 * @returns returns.messages - The array of SNS messages to send to the SNS topic.
 * @returns returns.messages[].payload - The content of the message (string).
 * @returns returns.messages[].subject - An optional subject of the message (string).
 */
function handler(input) {
  const messages = input.events.map((event) => ({
    payload: event,
  }));

  return {
    messages,
  };
}

For example, if the endpoint receives the following events:

{
  "eventType": "user.created",
  "payload": "{\"email\": \"joe@enterprise.io\"}"
}

{
  "eventType": "user.login", 
  "payload": "{\"id\": 12, \"timestamp\": \"2025-07-21T14:23:17.861Z\"}"
}

Using the same example events, the default SNS transformation would produce:

{
  "messages": [
    {
      "payload": {
        "eventType": "user.created",
        "payload": "{\"email\": \"joe@enterprise.io\"}"
      }
    },
    {
      "payload": {
        "eventType": "user.login",
        "payload": "{\"id\": 12, \"timestamp\": \"2025-07-21T14:23:17.861Z\"}"
      }
    }
  ]
}

To add a custom subject:

function handler(input) {
  const messages = input.events.map((event) => ({
    payload: event,
    subject: `Webhook: ${event.eventType}`,
  }));

  return {
    messages,
  };
}

This would produce:

{
  "messages": [
    {
      "payload": {
        "eventType": "user.created",
        "payload": "{\"email\": \"joe@enterprise.io\"}"
      },
      "subject": "Webhook: user.created"
    },
    {
      "payload": {
        "eventType": "user.login",
        "payload": "{\"id\": 12, \"timestamp\": \"2025-07-21T14:23:17.861Z\"}"
      },
      "subject": "Webhook: user.login"
    }
  ]
}