How to create subscription from an SNS to another SNS

Hello,

Tim here from the AWS Support Team. As of today’s date, 04/21/2022, SNS supports the following (I'll circle back to your question further down):

• Amazon Kinesis Data Firehose
• Amazon SQS
• AWS Lambda
• Email
• Email-JSON
• HTTP
• HTTPS
• Platform application endpoint
• SMS

For newer endpoints you can see the documentation here: https://docs.aws.amazon.com/sns/latest/dg/sns-create-subscribe-endpoint-to-topic.html

Now let’s circle back to your original question, can you add a SNS subscription to a SNS topic? Right now that isn't supported, however you could design workaround:

• SNS and fanout to an additional lambda function, and then write a bit of code to push it to another SNS topic.

However, I think there may be a better approach here, where instead of having items published to your first SNS topic, you:

• Publish it to EventBridge and fanout to multiple SNS resources. Would require a bit of testing to fully see if this is possible, but wanted to share it as a possible way forward. I viewed in my own EventBridge console if I could design an EventBridge rule with multiple SNS resources downstream and it appears possible, however I can't fully test all the quotas that would be specific to your application (you'd need to load test it and do careful examination of your system).

• Publish to an AWS Lambda function first, then have the Lambda function write to multiple SNS resources. Keep in mind quotas again here, so load test!

• The best option: wherever you're publishing messages to a SNS topic, just write it to the second SNS topic at the same time. I highly recommend this method. If a service is directly publishing to SNS so it's not some code doing the publishing, checkout EventBridge as a possible method again.

So to summarize a bit:

• No direct support right now, sorry about that!
• Workarounds exist, but takes careful evaluation and re-architecting. You'll want to keep in mind quotas, limits, throttling, for the specific workaround you choose.

Hope this helps out!